cp's OEIS Frontend

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.

A341510 Symmetric square array A(n,k) = A005940(1+A156552(n)+A156552(k)), read by antidiagonals starting with A(1,1).

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%I A341510 #24 Nov 09 2021 15:04:44
%S A341510 1,2,2,3,3,3,4,4,4,4,5,5,5,5,5,6,6,6,6,6,6,7,9,9,9,9,9,7,8,10,8,8,8,8,
%T A341510 10,8,9,7,15,7,7,7,15,7,9,10,8,10,12,10,10,12,10,8,10,11,15,7,15,25,
%U A341510 15,25,15,7,15,11,12,14,12,10,12,18,18,12,10,12,14,12,13,25,21,25,15,25,11,25,15,25,21,25,13
%N A341510 Symmetric square array A(n,k) = A005940(1+A156552(n)+A156552(k)), read by antidiagonals starting with A(1,1).
%C A341510 Considered as a binary operation on the positive integers, A(x, y) returns the term of the Doudna-sequence from the position that is the sum of the positions of x and y in the same sequence. (This is based on giving the Doudna-sequence an offset of 0, rather than 1 as used in A005940.) - _Peter Munn_, Feb 14 2021
%H A341510 Antti Karttunen, <a href="/A341510/b341510.txt">Table of n, a(n) for n = 1..10440; the first 144 antidiagonals of the array</a>
%H A341510 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%F A341510 A(n, k) = A(k, n) = A005940(1 + A156552(n) + A156552(k)).
%F A341510 A(n, n) = A003961(n).
%F A341510 A(n, 2*n) = A(2*n, n) = A329603(n).
%F A341510 A(n, 2) = A(2, n) = A297165(n).
%e A341510 The top left 16x16 corner of the array:
%e A341510    1,  2,  3,  4,  5,  6,  7,  8,  9, 10,  11,  12,  13,  14,  15, 16,
%e A341510    2,  3,  4,  5,  6,  9, 10,  7,  8, 15,  14,  25,  22,  21,  12, 11,
%e A341510    3,  4,  5,  6,  9,  8, 15, 10,  7, 12,  21,  18,  33,  20,  25, 14,
%e A341510    4,  5,  6,  9,  8,  7, 12, 15, 10, 25,  20,  27,  28,  35,  18, 21,
%e A341510    5,  6,  9,  8,  7, 10, 25, 12, 15, 18,  35,  16,  55,  30,  27, 20,
%e A341510    6,  9,  8,  7, 10, 15, 18, 25, 12, 27,  30,  11,  42,  45,  16, 35,
%e A341510    7, 10, 15, 12, 25, 18, 11, 16, 27, 14,  49,  20,  77,  50,  21, 24,
%e A341510    8,  7, 10, 15, 12, 25, 16, 27, 18, 11,  24,  21,  40,  49,  14, 45,
%e A341510    9,  8,  7, 10, 15, 12, 27, 18, 25, 16,  45,  14,  63,  24,  11, 30,
%e A341510   10, 15, 12, 25, 18, 27, 14, 11, 16, 21,  50,  35,  70,  75,  20, 49,
%e A341510   11, 14, 21, 20, 35, 30, 49, 24, 45, 50,  13,  36, 121,  22,  75, 32,
%e A341510   12, 25, 18, 27, 16, 11, 20, 21, 14, 35,  36,  45,  60, 125,  30, 75,
%e A341510   13, 22, 33, 28, 55, 42, 77, 40, 63, 70, 121,  60,  17,  98, 105, 48,
%e A341510   14, 21, 20, 35, 30, 45, 50, 49, 24, 75,  22, 125,  98,  33,  36, 13,
%e A341510   15, 12, 25, 18, 27, 16, 21, 14, 11, 20,  75,  30, 105,  36,  35, 50,
%e A341510   16, 11, 14, 21, 20, 35, 24, 45, 30, 49,  32,  75,  48,  13,  50, 81,
%o A341510 (PARI)
%o A341510 up_to = 105;
%o A341510 A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); (t); };
%o A341510 A156552(n) = { my(f = factor(n), p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res };
%o A341510 A341510sq(n,k) = A005940(1+A156552(n)+A156552(k));
%o A341510 A341510list(up_to) = { my(v = vector(up_to), i=0); for(a=1,oo, for(col=1,a, i++; if(i > up_to, return(v)); v[i] = A341510sq(col,(a-(col-1))))); (v); };
%o A341510 v341510 = A341510list(up_to);
%o A341510 A341510(n) = v341510[n];
%Y A341510 Cf. A341511 (the lower triangular section).
%Y A341510 Cf. A003961 (main diagonal), A329603 (skewed diagonal).
%Y A341510 Cf. A297165 (row 2 and column 2, when started from its term a(1)).
%Y A341510 Cf. also A003056, A268715, A341515, A341520, A348041.
%K A341510 nonn,tabl
%O A341510 1,2
%A A341510 _Antti Karttunen_, Feb 13 2021