A107414 - OEIS

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A107414

Least number k such that k*p(j)*p(j+1) - 1 and k*p(j)*p(j+1) + 1 are twin primes with p(j) and p(j+1) odd twin primes.

2, 12, 6, 60, 78, 336, 18, 216, 96, 144, 120, 18, 510, 516, 336, 66, 60, 420, 144, 570, 570, 270, 120, 156, 54, 102, 102, 540, 504, 48, 582, 264, 210, 156, 156, 78, 30, 282, 354, 240, 156, 372, 24, 102, 150, 180, 306, 690, 120, 210, 204, 252, 144, 156, 240, 156

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

2*3*5=30 29 and 31 twin primes, 3 and 5 first odd twin primes so k(1)=2

12*5*7=420 419 and 421 twin primes, 5 and 7 second odd twin primes so k(2)=12

6*11*13=858 857 and 859 twin primes, 11 and 13 third odd twin primes k(3)=6

MATHEMATICA

Module[{tp=Times@@@Select[Partition[Prime[Range[500]], 2, 1] , #[[2]]-#[[1]] == 2&], len, k}, len=Length[tp]; Table[k=1; While[!And@@PrimeQ[k*tp[[n]]+{1, -1}], k++]; k, {n, len}]] (* Harvey P. Dale, Mar 04 2013 *)

CROSSREFS

Sequence in context: A035877 A086494 A354484 * A133437 A245692 A182126

Adjacent sequences: A107411 A107412 A107413 * A107415 A107416 A107417

KEYWORD

easy,nonn

AUTHOR

Pierre CAMI, May 26 2005

STATUS

approved