id:A134532 - OEIS Search Results

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Numbers n such that the sum of the digits of 5^n is prime.

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4

1, 2, 4, 5, 6, 7, 13, 19, 20, 22, 26, 27, 29, 33, 34, 36, 41, 43, 44, 50, 54, 55, 58, 59, 60, 66, 69, 70, 74, 75, 81, 85, 91, 95, 97, 99, 100, 101, 110, 112, 125, 127, 129, 131, 133, 134, 136, 142, 143, 145, 146, 148, 153, 156, 157, 163, 165, 178, 187, 189, 190, 196 (list; graph; listen)

	OFFSET	`1,2`
	EXAMPLE	`5^2=25 and 2+5=7 is prime`
	MAPLE	`P:=proc(n) local cont, i, k, w; if isprime(n) then cont:=0; while cont<1000 do cont:=cont+1; w:=0; k:=n^cont; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if isprime(w) then print(cont); fi; od; fi; end: P(5);`
	CROSSREFS	`Cf. A076203, A134533, A134534, A134535.` `Adjacent sequences: A134529 A134530 A134531 this_sequence A134533 A134534 A134535` `Sequence in context: A070116 A039057 A092058 this_sequence A133398 A138836 A059921`
	KEYWORD	`easy,nonn,base`
	AUTHOR	`Paolo P. Lava & Giorgio Balzarotti (ppl(AT)spl.at), Oct 30 2007`

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Last modified January 8 02:43 EST 2009. Contains 152824 sequences.

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