A084709 a(1) = 4, for n > 1, a(n) = smallest multiple of a(n-1) such that a(n)-1 and a(n)+1 are twin primes.

4, 12, 60, 180, 1620, 9720, 417960, 7523280, 308454480, 25293267360, 1593475843680, 74893364652960, 4793175337789440, 517662936481259520, 21224180395731640320, 4075042635980474941440, 611256395397071241216000, 55624331981133482950656000

Offset

1,1

Links

Sean A. Irvine, Table of n, a(n) for n = 1..100

Mathematica

a[1] = 4; a[n_] := a[n] = Block[{k = 2}, While[ !PrimeQ[ k*a[n - 1] - 1] || !PrimeQ[ k*a[n - 1] + 1], k++ ]; k*a[n - 1]]; Table[ a[n], {n, 1, 17}]

Crossrefs

Sequence in context: A068525 A067755 A051858 * A057394 A054719 A356662

Adjacent sequences: A084706 A084707 A084708 * A084710 A084711 A084712

Keyword

nonn

Author

Amarnath Murthy, Jun 09 2003

Extensions

Edited and extended by Robert G. Wilson v, Jun 15 2003

More terms from Sean A. Irvine, May 04 2026

Status

approved