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A100557 Smallest prime of the form (prime(n)*prime(n+1)+q)/2 for some integer n and some prime q. 1
11, 19, 41, 73, 113, 163, 227, 337, 461, 577, 761, 883, 1013, 1249, 1567, 1801, 2053, 2381, 2593, 2887, 3299, 3697, 4337, 4919, 5231, 5519, 5843, 6173, 7177, 8363, 9007, 9533, 10357, 11251, 11863, 12799, 13613, 14447, 15493, 16223, 17291, 18433, 19013 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 2..1000

EXAMPLE

a(2) = 19 because 19 = (5*7 + 3)/2;

a(3) = 41 because 41 = (7*11 + 5)/2;

a(4) = 83 because 73 = (11*13 + 3)/2.

MATHEMATICA

f[n_] := Block[{k = 2, q = Prime[n]Prime[n + 1]}, While[p = Prime[k]; !PrimeQ[(q + p)/2], k++ ]; (q + p)/2]; Table[ f[n], {n, 2, 44}] (* Robert G. Wilson v, Nov 29 2004 *)

CROSSREFS

Sequence in context: A140506 A259190 A165944 * A066591 A061246 A068493

Adjacent sequences:  A100554 A100555 A100556 * A100558 A100559 A100560

KEYWORD

nonn,easy

AUTHOR

Giovanni Teofilatto, Nov 28 2004

EXTENSIONS

Edited, corrected and extended by Robert G. Wilson v, Nov 29 2004

STATUS

approved

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Last modified May 25 17:53 EDT 2020. Contains 334595 sequences. (Running on oeis4.)