[seqfan] Re: Prime partial sum of digits

[Eric Angelini]

Hello Bob,

> S = 2,1,4,6,40,20,46,8,4,24,60,...
> P = 2 3 7 1 11 11 22 3 4 44 55
>           3 77 99 39 7 1 37 33

... a(n) is the nth term of S [I hesitated naming it S(n)]
... P(4) is 13 (cumulative sum 2+1+4+6 = 13 --> to be read vertically under "6")

> Why does S(5) = 40 rather than 13?

... With S(5) = 13 we would have a non-prime cumulative sum for P(5) 
    as the "1" of "13" summated to P(4) would give the composite 14. 

Best (and sorry to be unclear),
É.

> Hi Eric,
>
>What is a(n)? Why does P(4) = 1?  Why does S(5) = 40 rather than 13?
>
>Cheers,
>Bob Selcoe