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A250478
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Number of times prime(n) occurs as the least prime factor among numbers 1 .. prime(n)^4: a(n) = A078898(A030514(n)).
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5
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8, 14, 42, 92, 305, 455, 944, 1238, 2085, 3995, 4710, 7757, 10273, 11558, 14742, 20701, 28019, 30444, 39680, 46534, 49856, 62350, 71394, 86977, 111352, 124421, 130649, 145076, 151939, 167759, 236113, 257098, 291830, 302611, 370060, 382610, 427214, 475078
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OFFSET
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1,1
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LINKS
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FORMULA
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a(1) = 1, a(n) = sum_{d | A002110(n-1)} moebius(d) * floor(prime(n)^3 / d). [Follows when A030514, prime(n)^4 is substituted to the similar formula given for A078898. Here A002110(n) gives the product of the first n primes. Because the latter is always squarefree, one could use here also Liouville's lambda (A008836) instead of Moebius mu (A008683).]
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PROG
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(PARI)
allocatemem(234567890);
A002110(n) = prod(i=1, n, prime(i));
A250478(n) = { my(p3); p3 = (prime(n)^3); sumdiv(A002110(n-1), d, (moebius(d)*(p3\d))); };
for(n=1, 23, print1(A250478(n), ", "));
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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