I recently bought a 17bii+ and had problems entering a formula that the solver would accept. I wrote HP, and this is their reply. I'm not sure I understand exactly what they are saying, but they seem to reflect the discussion on this forum recently about this problem. Their recommended solution DOES work, but I heard it first from Bruce, another member of this forum.

Hello Mr. Shepherd
Thank you for your support of HP Calculators.

My name is Rainer Boelzle and I am the HP Calculator WW TCE & Support
Manager. Thank you for your letter dated 2/24/2007. I forwarded your
email to our technical expert and he provided the following feedback:

-------------------------------

The user is entering the following formula:

0*L(A: LOG(N)+1)+
sigma(I :1:A:1:
MOD(N:10)+
0*L(N:IP(N/10)))

Which is semantically correct, but meaningless.

The reason for this is that: The variable A is a 'place holder', not a
real variable as it's value is changed all the time (by the L(A:
LOG(N)+1). The variable N, the input is also changed all the time by
the L(N:IP(N/10))

The solver will try to make the whole equation equal to 0, ie: Sum,
LOG(N)+1 times of ( N mod 10, with a division of N by 10 each time).
Ie, this equation calculates the sum of the digits in the integer part
of N.

However, as the solver is iterative (ie it will execute the equation
multiple times), after the first calculation, N will be equal to 0 and
the solver will stop with whatever value in A and 0 in N...

If the user really wants to calculate the sum of the digits of a number
he should do like this:

DIGITS=0*L(M:N)+sigma(I:1:LOG(N)+1:1:MOD(G(M):10)+0*L(M:IP(G(M)/10)))

And he will be able to enter a number in N and solve for digits and get
the sum of the digits of the number.

Note that he will not be able to do the reverse, ie: enter a value for
digits and find a number as this is not a continuous function and the
solver can not solve for that...

-------------------------------

I hope this helps. Please let me know if I can be of any further
assistance.

Thank you.

Rainer

Hewlett-Packard Company
16399 West Bernardo Drive, MS 8-600
San Diego, CA 92127
858-655-6737