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A122138 Indices n such that A122136[n] is a prime. 3
1, 2, 3, 4, 6, 8, 10, 11, 12, 14, 15, 18, 20, 22, 23, 26, 27, 32, 36, 38, 39, 40, 44, 47, 48, 50, 51, 52, 54, 55, 56, 58, 59, 60, 64, 66, 68, 71, 72, 74, 76, 78, 80, 83, 84, 86, 88, 89, 90, 92, 94, 95, 96, 98, 100, 102, 103, 107, 108, 110, 112, 114, 116, 118, 120, 122, 126 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A122136[n] = Numerator of Sum[ Prime[k]^2, {k,1,n}] / Product[ Prime[k], {k,1,n}] ] = Numerator[ A024450[n] / A002110[n] ]. A122136[n] begins {2,13,19,29,104,29,111,79,778,47,73,163,1068,359,5233,885,142,20477,219,811,...}. Corresponding primes such that A122136[ a(n) ] are listed in A122139[n] = {2,13,19,29,29,79,47,73,163,359,5233,20477,811,13859,2203,75997,3331,...}.

LINKS

Table of n, a(n) for n=1..67.

MATHEMATICA

Select[Range[200], PrimeQ[Numerator[Sum[Prime[k]^2, {k, 1, #1}]/Product[Prime[k], {k, 1, #1}]]]&]

CROSSREFS

Cf. A122136, A122137, A122139, A002110, A024450, A007504, A098999, A122102, A122103.

Sequence in context: A254438 A121539 A257457 * A047418 A026508 A184103

Adjacent sequences:  A122135 A122136 A122137 * A122139 A122140 A122141

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Aug 21 2006

STATUS

approved

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Last modified June 4 10:51 EDT 2020. Contains 334825 sequences. (Running on oeis4.)