A166686 Numbers m such that m plus the sum of the indices of the prime factors of the m-th composite (counted with multiplicity) is prime.

1, 2, 8, 9, 13, 14, 16, 17, 30, 31, 33, 34, 53, 59, 61, 65, 80, 85, 89, 92, 94, 96, 97, 103, 113, 116, 117, 121, 127, 128, 142, 143, 160, 163, 180, 182, 188, 189, 206, 208, 216, 221, 227, 235, 236, 242, 255, 256, 261, 262, 265, 271, 294, 297, 298, 300, 304, 315

Offset

1,2

Links

Table of n, a(n) for n=1..58.

Example

1st composite = 4 = 2*2 = (1st prime)*(1st prime) and 1+1+1=3 (prime), so 1 is in the sequence.
2nd composite = 6 = 2*3 = (1st prime)*(2nd prime) and 2+1+2=5 (prime), so 2 is in the sequence.

Crossrefs

Cf. A000040, A002808.

Sequence in context: A235524 A239133 A365517 * A064833 A281296 A073606

Adjacent sequences: A166683 A166684 A166685 * A166687 A166688 A166689

Keyword

nonn

Author

Juri-Stepan Gerasimov, Oct 18 2009

Extensions

6 removed, 49 removed, 94 inserted, 102 removed, 103 inserted by R. J. Mathar, Oct 28 2009

Definition reworded by Jon E. Schoenfield, Apr 15 2014

Status

approved