A124068 - OEIS

%I #19 Mar 31 2017 21:05:33

%S 0,1,1741725,4210818,9800817,9926315,14459929

%N Fixed points for operation of repeatedly replacing a number with the sum of the seventh power of its digits.

%C The sequence "Fixed points for operation of repeatedly replacing a number by the sum of the sixth power of its digits" has just 3 terms: 0, 1, and 548834.

%C For a d-digit number n >= 10^(d-1), the sum of 7th powers of its digits is <= 9^7*d, therefore these numbers cannot exceed 41205040. - _M. F. Hasler_, Apr 12 2015

%e 1741725 = 1^7 + 7^7 + 4^7 + 1^7 + 7^7 + 2^7 + 5^7.

%o (PARI) isok(n) = my(d = digits(n)); sum(k=1, #d, d[k]^7) == n; \\ _Michel Marcus_, Feb 21 2015

%o (PARI) for(n=0,41205040,A123253(n)==n&&print1(n",")) \\ _M. F. Hasler_, Apr 12 2015

%Y Cf. A046197, A052455, A052464, A124069, A226970, A003321.

%K base,fini,full,nonn

%O 1,3

%A _Sébastien Dumortier_, Nov 05 2006