Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #37 Jul 18 2021 03:04:11
%S 125,142,1005,118678,706862,18481615,122003411,30330043,5923078409,
%T 22110133333,120175787632,5971473681952
%N a(n) is the smallest number k such that the sum of the n-th powers of the digits of k equals the sum of the divisors of k other than 1 and k.
%e a(5) = 118678 because 1^5 + 1^5 + 8^5 + 6^5 + 7^5 + 8^5 = 90121, and sum of the divisors 1 < d < a(5) = sigma(118678) - 118678 - 1 = 90121.
%o (PARI) f(k, n) = my(d=digits(k)); sum(i=1, #d, d[i]^n);
%o a(n) = my(k=1); while(f(k, n) != sigma(k)-k-1, k++); k; \\ _Michel Marcus_, Sep 29 2018
%Y Cf. A070308 (n=2, "Canada perfect numbers").
%Y Cf. A202279 (n=3), A202147 (n=4), A202285 (n=5).
%K nonn,hard,base,more
%O 2,1
%A _Michel Lagneau_, Dec 16 2011
%E a(8)-a(9) added by _Amiram Eldar_, Sep 29 2018
%E a(10)-a(13) from _Giovanni Resta_, Oct 04 2018