A209048 Indices of the pentagonal numbers listed in A209049.

1, 2, 4, 3, 12, 11, 32, 27, 75, 192, 427, 171, 1323, 2187, 6912, 8192, 4779, 10923, 49152, 109227, 60075, 170667, 786432, 699051, 1092267, 4893355, 5810859, 11184811, 25864875, 95070891, 101362347, 44739243

Offset

0,2

Comments

Pentagonal analog of A076550.

Links

Table of n, a(n) for n=0..31.

Mathematica

k = 1; t = Table[0, {50}]; While[k < 500000001, a = PrimeOmega[k] + PrimeOmega[3 k - 1] - 1; If[ t[[a + 1]] == 0, t[[a + 1]] = k; Print[{k, a}]]; k++]; t

Crossrefs

A209049, A076550.

Sequence in context: A259630 A114883 A125091 * A181327 A257503 A091861

Adjacent sequences: A209045 A209046 A209047 * A209049 A209050 A209051

Keyword

nonn

Author

Robert G. Wilson v, Mar 04 2012

Status

approved