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A036878 Integers of the form p^(p-1), where p is prime. 8
2, 9, 625, 117649, 25937424601, 23298085122481, 48661191875666868481, 104127350297911241532841, 907846434775996175406740561329, 88540901833145211536614766025207452637361 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also the least refactorable number (A033950) k has the n-th prime as its least prime factor. - Robert G. Wilson v, Jun 28 2006

Integers equal to the product of their cototient and their number of divisors: A051953(p^(p-1)) = p^(p-2), A000005(p^(p-1)) = p and p^(p-2)*p = p^(p-1). # Paolo P. Lava, Jan 23 2019

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..77

S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2.

S. Colton, HR - Automatic Theory Formation in Pure Mathematics

EXAMPLE

5^{5-1} = 5^4 = 625.

MATHEMATICA

Table[Prime@n^(Prime@n - 1), {n, 10}] (* Robert G. Wilson v, Jun 28 2006 *)

#^(#-1)&/@Prime[Range[10]] (* Harvey P. Dale, Oct 23 2015 *)

PROG

(MAGMA) [p^(p-1): p in PrimesUpTo(50)]; // Vincenzo Librandi, Mar 27 2014

(PARI) a(n) = my(p=prime(n)); p^(p-1); \\ Michel Marcus, Jan 24 2019

CROSSREFS

These integers are refactorable - i.e., the number of divisors divides the number itself, cf. A033950.

Subset of A062981. Subsequence of A000169.

Sequence in context: A086693 A085605 A180936 * A162710 A249903 A008322

Adjacent sequences:  A036875 A036876 A036877 * A036879 A036880 A036881

KEYWORD

nonn,easy

AUTHOR

Simon Colton (simonco(AT)cs.york.ac.uk)

STATUS

approved

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Last modified May 25 00:59 EDT 2019. Contains 323534 sequences. (Running on oeis4.)