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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. 1
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: A345469 A035877 A086494 * A133437 A245692 A182126

Adjacent sequences:  A107411 A107412 A107413 * A107415 A107416 A107417

KEYWORD

easy,nonn

AUTHOR

Pierre CAMI, May 26 2005

STATUS

approved

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Last modified October 22 18:45 EDT 2021. Contains 348175 sequences. (Running on oeis4.)