A248554 Numbers k such that the sum of the digital roots of the first k primes is also prime; increasingly sorted.

1, 2, 4, 5, 6, 7, 9, 11, 17, 37, 41, 47, 59, 61, 79, 85, 87, 98, 104, 109, 112, 126, 132, 141, 142, 143, 151, 152, 158, 173, 183, 184, 191, 192, 204, 208, 210, 212, 215, 221, 226, 227, 236, 243, 251, 256, 274, 279, 306, 314, 325, 334, 356, 365, 375, 382, 387, 401, 403, 419, 437, 452, 473, 483, 488

Offset

1,2

Links

Ivan N. Ianakiev, Table of n, a(n) for n = 1..1000

Example

The sum of the digital roots of the first four primes is prime (2+3+5+7=17), therefore 4 is in the sequence.

Mathematica

Select[Range[1000], PrimeQ[Sum[Mod[Prime[i], 9], {i, 1, #}]]&]

Crossrefs

Cf. A000040, A010888.

Sequence in context: A164317 A138620 A260820 * A346993 A098166 A217445

Adjacent sequences: A248551 A248552 A248553 * A248555 A248556 A248557

Keyword

base,easy,nonn

Author

Ivan N. Ianakiev, Oct 08 2014

Extensions

Edited. Name specified. - Wolfdieter Lang, Oct 30 2014

Status

approved