This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A277289 #38 Oct 14 2016 17:16:43 %S A277289 1,2,4,5,8,25,44,4664,6568,1353025,2919526,5709589,7827725,64661225, %T A277289 85132756,153872408,743947534,34304296003,38832409867,40263727492, %U A277289 1946603375348,2469908330348,64471909888247,274267749806485,888906849689897,896501949422459 %N A277289 Positive integers n such that n | (3^n + 7). %C A277289 No other terms below 10^15. - _Max Alekseyev_, Oct 14 2016 %C A277289 492385451091805616444 is a term. %e A277289 3^25 + 7 = 847288609450 = 25 * 33891544378, so 25 is a term. %o A277289 (PARI) is(n)=Mod(3,n)^n==-7; \\ _Joerg Arndt_, Oct 09 2016 %o A277289 (Python) A277289_list = [1,2,4,5]+[n for n in range(6,10**6) if pow(3,n,n)==n-7] # _Chai Wah Wu_, Oct 12 2016 %Y A277289 Solutions to 3^n == k (mod n): A277340 (k=-11), this sequence (k=-7), A277288 (k=-5), A015973 (k=-2), A015949 (k=-1), A067945 (k=1), A276671 (k=2), A276740 (k=5), A277126 (k=7), A277274 (k=11). %K A277289 nonn %O A277289 1,2 %A A277289 _Seiichi Manyama_, Oct 09 2016 %E A277289 a(17) from _Joerg Arndt_, Oct 09 2016 %E A277289 a(18)-a(20) from _Chai Wah Wu_, Oct 12 2016 %E A277289 a(21)-a(26) from _Max Alekseyev_, Oct 14 2016