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 A350066 Symmetric square array A(n,k) = A122111(A122111(n) * A122111(k)), n >= 1, k >= 1, read by antidiagonals. 5
 1, 2, 2, 3, 3, 3, 4, 5, 5, 4, 5, 6, 7, 6, 5, 6, 7, 10, 10, 7, 6, 7, 10, 11, 9, 11, 10, 7, 8, 11, 14, 14, 14, 14, 11, 8, 9, 12, 13, 15, 13, 15, 13, 12, 9, 10, 15, 20, 22, 22, 22, 22, 20, 15, 10, 11, 14, 21, 18, 17, 21, 17, 18, 21, 14, 11, 12, 13, 22, 25, 28, 26, 26, 28, 25, 22, 13, 12, 13, 20, 17, 21, 33, 30, 19, 30, 33, 21, 17, 20, 13 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A122111 is a self-inverse permutation, so this array represents a binary operation A(.,.) over the positive integers that is isomorphic to multiplication. Its primes are the positive powers of 2 (as defined by standard multiplication): 2, 4, 8, 16, 32, ... . The positive powers of 2, as defined by A(.,.), are the prime numbers as we usually understand them: 2, 3, 5, 7, 11, ... . - Peter Munn, Aug 04 2022 LINKS FORMULA A(n, A061142(n)) = A003961(n). - Peter Munn, Aug 04 2022 EXAMPLE The top left 15 X 15 corner of the array:    1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11,  12, 13, 14,  15,    2,  3,  5,  6,  7, 10, 11, 12, 15, 14, 13,  20, 17, 22,  21,    3,  5,  7, 10, 11, 14, 13, 20, 21, 22, 17,  28, 19, 26,  33,    4,  6, 10,  9, 14, 15, 22, 18, 25, 21, 26,  30, 34, 33,  35,    5,  7, 11, 14, 13, 22, 17, 28, 33, 26, 19,  44, 23, 34,  39,    6, 10, 14, 15, 22, 21, 26, 30, 35, 33, 34,  42, 38, 39,  55,    7, 11, 13, 22, 17, 26, 19, 44, 39, 34, 23,  52, 29, 38,  51,    8, 12, 20, 18, 28, 30, 44, 27, 50, 42, 52,  45, 68, 66,  70,    9, 15, 21, 25, 33, 35, 39, 50, 49, 55, 51,  70, 57, 65,  77,   10, 14, 22, 21, 26, 33, 34, 42, 55, 39, 38,  66, 46, 51,  65,   11, 13, 17, 26, 19, 34, 23, 52, 51, 38, 29,  68, 31, 46,  57,   12, 20, 28, 30, 44, 42, 52, 45, 70, 66, 68,  63, 76, 78, 110,   13, 17, 19, 34, 23, 38, 29, 68, 57, 46, 31,  76, 37, 58,  69,   14, 22, 26, 33, 34, 39, 38, 66, 65, 51, 46,  78, 58, 57,  85,   15, 21, 33, 35, 39, 55, 51, 70, 77, 65, 57, 110, 69, 85,  91, PROG (PARI) up_to = 105; A122111(n) = if(1==n, n, my(f=factor(n), es=Vecrev(f[, 2]), is=concat(apply(primepi, Vecrev(f[, 1])), [0]), pri=0, m=1); for(i=1, #es, pri += es[i]; m *= prime(pri)^(is[i]-is[1+i])); (m)); A350066sq(n, k) = A122111(A122111(n)*A122111(k)); A350066list(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] = A350066sq(col, (a-(col-1))))); (v); }; v350066 = A350066list(up_to); A350066(n) = v350066[n]; \\ Antti Karttunen, Dec 13 2021 CROSSREFS Cf. A122111, A297002 (main diagonal), A253550 (after its initial term, gives row 2 / column 2 from the second term onward). See the formula section for the relationships with A003961, A061142. Cf. also A003991, A129595, A331590. Sequence in context: A124882 A262518 A085578 * A135646 A334922 A301851 Adjacent sequences:  A350063 A350064 A350065 * A350067 A350068 A350069 KEYWORD nonn,tabl,changed AUTHOR Antti Karttunen, Dec 13 2021 STATUS approved

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Last modified August 14 03:43 EDT 2022. Contains 356110 sequences. (Running on oeis4.)