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1, 2, 4, 5, 10, 12, 15, 20, 24, 27, 28, 56, 57, 114, 116, 145, 150, 156, 169, 170, 340, 341, 682, 684, 855, 860, 1032, 1035, 1150, 1152, 1161, 1204, 1232, 1243, 1356, 1368, 1387, 1460, 1480, 1517, 1558, 1596, 1617, 1628, 1776, 1779, 2372, 2376, 2673, 2674
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OFFSET
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1,2
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COMMENTS
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a(n) is odd iff n mod 3 = 1. Parity of a(n) is related to that of A351743(n).
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LINKS
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FORMULA
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Conjecture: a(n + 42) = 3645*a(n) + b(n) for n >= 138 (where b is 42-periodic).
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EXAMPLE
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MATHEMATICA
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nn = 50, a[1] = m = s = 1; Do[If[m == 1, Set[k, s], Set[k, s]; While[GCD[m, k] > 1, k /= GCD[m, k]]]; m = k; s += k; a[n] = s, {n, 2, nn}]; Array[a, nn]
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PROG
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(PARI) { s=0; for (n=1, 50, if (n==1, v=1, w=s; while (1 < g=gcd(w, v), w /= g); v=w); print1 (s+=v", ")) }
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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