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A098142 Numbers n such that (p*(q-1)+(p-1)*q)/2 is prime, where p and q are consecutive odd primes, p<q and p_n is the n-th prime. 2
2, 3, 5, 9, 13, 15, 17, 26, 35, 43, 56, 60, 80, 81, 83, 86, 89, 101, 102, 104, 120, 140, 152, 157, 170, 178, 191, 201, 204, 215, 219, 223, 238, 252, 286, 293, 296, 324, 329, 350, 359, 373, 383, 392, 395, 398, 412, 416, 424, 444, 458, 468, 479, 487, 497, 503, 514 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..57.

MATHEMATICA

f[n_] := Block[{p = Prime[n], q = Prime[n + 1]}, r = (p*(q - 1) + (p - 1)*q)/2; If[ PrimeQ[r], r, 0]]; Select[ Range[522], f[ # ] != 0 &]

CROSSREFS

The generator of A099911.

Sequence in context: A245905 A087146 A033945 * A270812 A066821 A108568

Adjacent sequences:  A098139 A098140 A098141 * A098143 A098144 A098145

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller and Robert G. Wilson v, Nov 02 2004

STATUS

approved

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Last modified October 23 11:19 EDT 2019. Contains 328345 sequences. (Running on oeis4.)