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A209048 Indices of the pentagonal numbers listed in A209049. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 28 12:58 EST 2020. Contains 331321 sequences. (Running on oeis4.)