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A212648 Minimal m>=0 such that (2*n-1)!!-2^m is prime. 2
0, 1, 1, 2, 2, 2, 1, 1, 1, 6, 9, 2, 6, 6, 8, 16, 2, 15, 6, 3, 3, 5, 7, 26, 1, 8, 16, 18, 7, 14, 12, 9, 5, 14, 8, 1, 32, 7, 2, 2, 3, 53, 8, 1, 3, 10, 10, 20, 8, 25, 20, 2, 23, 7, 13, 21, 87, 16, 76, 35, 30, 18, 12, 7, 1, 117, 36, 40, 57, 25, 3, 5, 47, 62 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,4

LINKS

Table of n, a(n) for n=2..75.

MATHEMATICA

a[n_] := Block[{f=(2*n-1)!!, m=0}, While[! PrimeQ[f - 2^m], m++]; m]; a /@ Range[2, 75] (* Giovanni Resta, Feb 14 2013 *)

CROSSREFS

Cf. A212281, A212282, A212321, A212636, A212637.

Sequence in context: A253187 A139755 A213366 * A255507 A195052 A104637

Adjacent sequences:  A212645 A212646 A212647 * A212649 A212650 A212651

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Feb 14 2013

EXTENSIONS

a(8)-a(75) from Giovanni Resta, Feb 14 2013

STATUS

approved

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Last modified May 24 06:53 EDT 2019. Contains 323529 sequences. (Running on oeis4.)