A166686 - OEIS

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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

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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