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 A384310 #29 Jun 10 2025 00:37:47 %S A384310 0,3,6,7,12,20,26,27,28,53,56,61,74,88,145,146,252,289,299,308,320, %T A384310 323,340,471,577,578,739,1240,1517,1568,1579,1857,2638,3042,3043,3133, %U A384310 3455,3565,4910,8683,8684,8857,8858,9291,14549,17913,18117,20005,21989,32552,37902,42514,44869,47877,49942 %N A384310 Numbers k such that A383844(k) and A383844(k+1) are nonzero. %C A384310 a(n) is the lesser term of a pair of consecutive nonzero terms in A383844. %C A384310 Triplets of consecutive nonzero terms can also be found in A383844 and are represented here as pairs. Up to n = 83354 there are 8 such triplets, the least terms of each being 6, 26, 27, 145, 577, 3042, 8683, 8857. %e A384310 26 is a term since A383844(26) and A383844(27) are nonzero. %e A384310 27 is a term since A383844(27) and A383844(28) are nonzero. %e A384310 252 is a term since A383844(252) and A383844(253) are nonzero. %e A384310 61890 is a term since A383844(61890) and A383844(61891) are nonzero. %o A384310 (PARI) isok(n) = (count(n) = my(f, S=[], b);(f(m)=my(r=0); forprime(p=2, m, r+=m%p); return(r)); if(n<=21, b=26); if(n>21, b=n); if(n>=250, b=n^0.8); if(n>=6000, b=n^0.7); if(n>=21000, b=n^0.68); if(n>=43000, b=n^0.67); for(k=0, b, if(f(k)==n, S=concat(S,k))); return(S)); if(n==0 || (n>1 && count(n)<>[] && count(n+1)<>[]), return(1), return(0)) %Y A384310 Cf. A024934, A383844. %K A384310 nonn %O A384310 1,2 %A A384310 _Miles Englezou_, Jun 04 2025