A096983 a(n) is the smallest prime whose base-n digits add up to a composite number.

23, 233, 7, 73, 11, 4801, 11, 17, 13, 19, 17, 337, 17, 23, 19, 31, 23, 151, 23, 29, 29, 31, 29, 73, 29, 41, 31, 37, 37, 619, 37, 41, 37, 43, 41, 61, 41, 47, 43, 61, 47, 67, 47, 53, 53, 61, 53, 73, 53, 59, 59, 61, 59, 79, 59, 71, 61, 67, 67, 109, 67, 71, 67, 73, 71, 101, 71, 83

Offset

2,1

Comments

Inspired by a homework problem in Crandall and Pomerance, Prime Numbers.

Links

Table of n, a(n) for n=2..69.

Example

23 = 10111 (base 2) and 1+1+1+1=4, 233 = 22122 (base 3) and 2+2+1+2+2=9, 337 = 1,12,12 (base 13) and 1+12+12=25.

Mathematica

f[n_] := Block[{p = PrimePi[n] + 1}, While[ PrimeQ[Plus @@ IntegerDigits[Prime[p], n]], p++ ]; Prime[p]]; Table[ f[n], {n, 2, 70}] (* Robert G. Wilson v, Aug 21 2004 *)

Crossrefs

Sequence in context: A022715 A060189 A028824 * A140572 A140844 A168438

Adjacent sequences: A096980 A096981 A096982 * A096984 A096985 A096986

Keyword

nonn,base

Author

John L. Drost, Aug 19 2004

Extensions

More terms from Robert G. Wilson v, Aug 21 2004

Status

approved