A075539 Perfect powers n such that (n-5)/2 is prime.

9, 27, 2187, 19683, 300763, 1092727, 2048383, 6128487, 15069223, 21717639, 24642171, 27818127, 36264691, 38958219, 54439939, 65450827, 84604519, 90224199, 112678587, 133432831, 139798359, 143055667, 163667323, 246491883, 313046839, 341532099, 347428927

Offset

1,1

Links

Table of n, a(n) for n=1..27.

Example

9=3^2, 27=3^3, 2187=3^7, 19683=3^9, but 300763=67^3 - is there any rule?

Mathematica

pp = Join[{1}, Select[ Range[10^7], Apply[GCD, Last[ Transpose[ FactorInteger[ # ]]]] > 1 & ]]; Select[pp, PrimeQ[(# - 5)/2] & ]

Crossrefs

Sequence in context: A020254 A124396 A020281 * A225300 A053825 A328640

Adjacent sequences: A075536 A075537 A075538 * A075540 A075541 A075542

Keyword

easy,nonn

Author

Zak Seidov, Oct 11 2002

Extensions

Extended by Robert G. Wilson v, Oct 14 2002

More terms from Sean A. Irvine, Feb 24 2025

Status

approved