A097421 a(n) = (5^(2^n) - 1)/2^(n+2).

1, 3, 39, 12207, 2384185791, 181898940354585647583, 2117582368135750847670806251699104905128479, 573971850987445072250359637315549647372395291392620860111695169081258427468128502368927

Offset: 0

Author

Lekraj Beedassy, Aug 21 2004

Keywords

• nonn

Crossrefs

Cf. A070632.

Programs

Mathematica

Table[(5^(2^n)-1)/2^(n+2),{n,0,10}] (* Harvey P. Dale, Aug 07 2025 *)