cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A114484 Number of decimal digits in Fermat(10^n).

Original entry on oeis.org

1, 309, 381600854690147056244358827361
Offset: 0

Views

Author

Eric W. Weisstein, Nov 30 2005

Keywords

Comments

Next term a(3) has 301 digits.

Crossrefs

Subsequence of A057755. - Arkadiusz Wesolowski, Jun 30 2011

Programs

  • Mathematica
    Block[{$MaxExtraPrecision = Infinity}, Table[1 + Floor[2^10^n Log[10, 2]], {n, 0, 2}]]

Formula

a(n) = A057755(10^n) = A055642(A000215(A011557(n))). - Amiram Eldar, Jul 17 2025

A108301 Digital sum of the Fermat number 2^(2^n) + 1.

Original entry on oeis.org

3, 5, 8, 14, 26, 59, 89, 167, 377, 734, 1376, 2741, 5624, 11120, 22166, 44222, 88262, 176180, 353042, 707648, 1419974, 2836751, 5679620, 11365592, 22723865, 45445442, 90899234, 181828850
Offset: 0

Views

Author

Jason Earls, Jun 29 2005

Keywords

Comments

a(0), a(1), a(5), a(6), a(7) and a(11) are primes. Are there any more?

Examples

			a(5)=59 because 2^(2^5) + 1 = 4294967297 and the sum of those decimal digits is 59.
		

Crossrefs

Cf. A000215.

Programs

  • Maple
    a:=proc(n) local nn, z: nn:=convert(2^(2^n)+1,base,10): z:=nops(nn): add(nn[j],j=1..z) end: seq(a(n),n=0..22); # Emeric Deutsch
  • Mathematica
    f[n_] := Plus @@ IntegerDigits[2^(2^n)] + 1; Table[ f[n], {n, 0, 27}] (* Robert G. Wilson v, Jul 02 2005 *)

Formula

a(n) = ~4.5*A057755. - Robert G. Wilson v, Jul 02 2005

Extensions

More terms from Emeric Deutsch and Robert G. Wilson v, Jul 02 2005
Showing 1-2 of 2 results.