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 A379802 #19 Feb 09 2025 12:13:27 %S A379802 2,12,31,60,90,132,183,241,307,380,462,552,677,997,1125,1444,1563, %T A379802 1722,1892,2117,2257,2450,2652,2914,3081,3306,3540,3782,4033,4291, %U A379802 4560,4830,5112,5403,5701,6006,6320,6643,6972,7311,7657,8464,8743,9121,9506,9902,11238,12100,12542,12883,15877,16257,17424,17823,18361,18906,19462 %N A379802 Indices k such that A377091(k) is immediately followed by A377091(k+1) = -A377091(k). %H A379802 Rémy Sigrist, <a href="/A379802/b379802.txt">Table of n, a(n) for n = 1..10000</a> (first 209 terms from N. J. A. Sloane) %H A379802 Rémy Sigrist, <a href="/A379802/a379802.txt">C++ program</a> %e A379802 Terms 0 through 14 of A377091 are 0, 1, 2, -2, -1, 3, 4, 5, -4, -3, 6, 7, 8, -8, -7, and the pairs 2, -2 and 8, -8 correspond to a(1) = 2 and a(2) = 12. %t A379802 (* A377091list is defined at A377091 *) %t A379802 PositionIndex[Differences[Abs[A377091list[10000]]]][0] - 1 (* _Paolo Xausa_, Jan 22 2025 *) %o A379802 (C++) // See Links section. %Y A379802 Cf. A377091, A379066, A379788-A379794, A379803, A379804, A380837. %K A379802 nonn %O A379802 1,1 %A A379802 _N. J. A. Sloane_, Jan 19 2025