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 A117348 #25 Feb 16 2025 08:33:00 %S A117348 6,10,20,28,70,88,104,110,120,136,152,464,496,592,650,672,884,1155, %T A117348 1888,1952,2144,4030,5830,8128,8384,8925,11096,17816,18632,18904, %U A117348 30240,32128,32445,32760,32896,33664,45356,70564,77744,85936,91388,100804,116624 %N A117348 Near-multiperfects with primes and powers of 2 excluded, abs(sigma(m) mod m) <= log(m). %C A117348 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 A117348 R. K. Guy, Unsolved Problems in Number Theory, B2. %H A117348 Amiram Eldar, <a href="/A117348/b117348.txt">Table of n, a(n) for n = 1..10000</a> %H A117348 Walter Nissen, <a href="http://upforthecount.com/math/nearmpf.html">Near Multiperfects</a>. %H A117348 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MultiperfectNumber.html">Multiperfect Number</a> %F A117348 sigma(n) = k * n + r, abs(r) <= log(n). %e A117348 70 is a term because sigma(70) = 144 = 2 * 70 + 4, while 4 < log (70) ~= 4.248. %Y A117348 Cf. A045768, A045769, A045770, A077374, A087167, A087485. %Y A117348 Cf. A088007, A088008, A088010, A088011, A088012. %Y A117348 Cf. A117346, A117347, A117349, A117350. %K A117348 nonn %O A117348 1,1 %A A117348 _Walter Nissen_, Mar 09 2006 %E A117348 Offset corrected by _Amiram Eldar_, Mar 05 2020