A125724 If "sumdigit" denotes the sum of the digits of a number then these are the numbers n such that n=sumdigit(sumdigit(n)^sumdigit(n)).

1, 13, 25, 45, 58, 88, 98

Offset: 1

Author

Paolo P. Lava and Giorgio Balzarotti, Feb 02 2007

Keywords

• easy
• fini
• full
• nonn
• base

Comments

Sequence is complete. - Giovanni Resta, Mar 21 2013

Examples

			sumdigit(13)=4; 4^4 = 256; sumdigit(256)=13
		

Crossrefs

Cf. A125526.

Programs

Maple

P:=proc(n) local i,j,k,w; for i from 1 by 1 to n do w:=0; k:=i; while k>0 do w:=w+k-trunc(k/10)*10; k:=trunc(k/10); od; k:=w^w; w:=0; while k>0 do w:=w+k-trunc(k/10)*10; k:=trunc(k/10); od; if (i=w) then print(i,w); fi; od; end: P(100);

Mathematica

sdQ[n_]:=Module[{sd=Total[IntegerDigits[n]]},n==Total[ IntegerDigits[ sd^sd]]]; Select[Range[100],sdQ] (* Harvey P. Dale, Oct 22 2013 *)