A020645 - OEIS

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A020645

Least positive integer k for which 4^n divides k!.

1, 4, 6, 8, 10, 12, 16, 16, 18, 20, 24, 24, 28, 30, 32, 32, 34, 36, 40, 40, 44, 46, 48, 48, 52, 54, 56, 58, 60, 64, 64, 64, 66, 68, 72, 72, 76, 78, 80, 80, 84, 86, 88, 90, 92, 96, 96, 96, 100, 102, 104, 106, 108, 112, 112, 114, 116, 120, 120, 124, 126, 128, 128, 128, 130, 132, 136

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OFFSET

0,2

LINKS

T. D. Noe, Table of n, a(n) for n = 0..1000

PROG

(PARI) a(n) = {k = 1; fk = 1; while (valuation(fk, 4) < n, k++; fk *= k); k; } \\ Michel Marcus, Aug 20 2013

CROSSREFS

Sequence in context: A310658 A167179 A193167 * A053226 A227112 A051756

Adjacent sequences: A020642 A020643 A020644 * A020646 A020647 A020648

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved