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 A117350 #27 Feb 16 2025 08:33:00 %S A117350 70,110,120,650,672,884,1155,4030,5830,8925,11096,17816,18632,18904, %T A117350 30240,32445,32760,45356,70564,77744,85936,91388,100804,116624,244036, %U A117350 254012,388076,391612,430272,442365,523776,1090912,1848964,2178540 %N A117350 Near-multiperfects with primes, powers of 2, 6 * prime and 2^n * prime excluded, abs(sigma(n) mod n) <= log(n). %C A117350 Sequences A117346 through A117350 are an attempt to improve on sequences A045768 through A045770, A077374, A087167, A087485 and A088007 through A088012 and related sequences (but not to replace them) by using a more significant definition of "near." E.g., is sigma (n) really "near" a multiple of n, for n=9? Or n=18? Sigma is the sum_of_divisors function. %D A117350 R. K. Guy, Unsolved Problems in Number Theory, B2. %H A117350 Donovan Johnson, <a href="/A117350/b117350.txt">Table of n, a(n) for n = 1..114</a> (terms <= 10^12) %H A117350 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MultiperfectNumber.html">Multiperfect Number</a>. %e A117350 70 is in the sequence because sigma(70) = 144 = 2*70 + 4, while 4 < log(70) ~= 4.248. %e A117350 The 2-perfect numbers are excluded because they are 2^n * prime. %Y A117350 Cf. A045768 through A045770, A077374, A087167, A087485, A088007 through A088012, A117346 through A117349. %K A117350 nonn %O A117350 1,1 %A A117350 _Walter Nissen_, Mar 09 2006 %E A117350 Offset corrected by _Donovan Johnson_, Oct 01 2012