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A100930 Semiprimes of the form (2*p+1)*(p-1)/2, p prime. 1
22, 115, 517, 6847, 31951, 128701, 516601, 1037851, 2070001, 4156501, 4254937, 6045451, 7945351, 8425957, 8777887, 9137017, 13124317, 14278951, 14460907, 14920837, 24194101, 29146501, 31795501, 47592751, 48758797, 50108701 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = (2*A059455(n)^2 - A059455(n) - 1) / 2.

LINKS

Table of n, a(n) for n=1..26.

Eric Weisstein's World of Mathematics, Semiprime

Eric Weisstein's World of Mathematics, Sophie Germain Prime

CROSSREFS

Subsequence of A100929.

Cf. A001358, A005384, A005385.

Sequence in context: A074277 A299580 A289350 * A260810 A274610 A290800

Adjacent sequences:  A100927 A100928 A100929 * A100931 A100932 A100933

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 22 2004

STATUS

approved

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Last modified February 19 22:38 EST 2019. Contains 320328 sequences. (Running on oeis4.)