A065895 Which composite number is n^n ?: a(n) = k such that A002808(k) = n^n, or 0 if n^n is not composite.

0, 1, 17, 201, 2679, 41834, 757857, 15699344, 366719682, 9544947488, 274049557236, 8606313278052, 293501427948319, 10802628699872589, 426834313802135110, 18021087789674333872, 809692585861972457700, 38575004548436059251080, 1942399549000209200252133

Offset

1,3

Links

Table of n, a(n) for n=1..19.

Formula

a(n) = n^n - A064151(n) - 1. - Amiram Eldar, Aug 09 2024

Example

For n = 3: 3^3 = 27 = A002808(17) is the 17th composite number.

Mathematica

Table[n^n - PrimePi[n^n] - 1, {n, 1, 12}]

Prog

(PARI) a(n) = my(m = n^n); m - primepi(m) - 1; \\ Amiram Eldar, Aug 09 2024

Crossrefs

Cf. A000312, A000720, A002808, A064151.

Sequence in context: A201258 A166216 A021134 * A009479 A279448 A017897

Adjacent sequences: A065892 A065893 A065894 * A065896 A065897 A065898

Keyword

nonn

Author

Labos Elemer, Nov 28 2001

Extensions

More terms from Robert G. Wilson v and Vladeta Jovovic, Nov 29 2001

Name clarified and a(13)-a(19) calculated from the data at A064151 and added by Amiram Eldar, Aug 09 2024

Status

approved