A110742 Number of primes with digit sum n having at most n digits.

0, 2, 1, 8, 27, 0, 211, 500, 0, 5404, 23137, 0, 269736, 806856, 0, 10508986, 43103947, 0

Offset

1,2

Comments

a(3n) = 0 for n > 1.

The binary version of this sequence is the characteristic function of A000043. [David Wasserman, Dec 17 2008]

Links

Table of n, a(n) for n=1..18.

Example

For a(2) the two primes are 2 and 11. 101 is not included because it has 3 digits.

Prog

(PARI) f(n, i, left, num) = if (i == n - 1, return(left <= 9 && isprime(num + left*10^i))); sum(j = 0, min(left, 9), f(n, i + 1, left - j, num + j*10^i));
a(n) = f(n, 0, n, 0); \\ David Wasserman, Dec 17 2008

Crossrefs

Cf. A110741.

Sequence in context: A160602 A160626 A052312 * A252355 A366404 A013123

Adjacent sequences: A110739 A110740 A110741 * A110743 A110744 A110745

Keyword

base,nonn,more

Author

Amarnath Murthy, Aug 10 2005

Extensions

a(7)-a(10) from Donovan Johnson, Mar 23 2008

More terms from David Wasserman, Dec 17 2008

Status

approved