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Search: id:A035527
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| 1, 6, 28, 270, 496, 672, 1638, 6200, 8128, 18620, 30240, 32760, 173600, 1089270, 2229500, 2457000, 4713984, 6051500, 8506400, 17428320, 23088800, 29410290, 33550336, 45532800, 52141320, 81695250, 115048440, 142990848, 255428096
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OFFSET
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0,2
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COMMENT
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A harmonic number is a harmonic seed if it does not have a proper unitary divisor (a divisor d such that gcd(d,n/d)=1) which is harmonic.
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REFERENCES
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G. L. Cohen and R. M. Sorli, Harmonic Seeds, Fibonacci Quarterly, Vol. 36, No. 5 (1998), Pg. 386-390 MR1657575 (99j:11002)
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PROGRAM
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(PARI) harm(n)=if(n<1, 0, 0==(sigma(n, 0)*n)%sigma(n, 1)) {a(n)=local(t); if(n<0, 0, n=a(n-1); until(if(t=1, if(harm(n), fordiv(n, d, t*=((d==n)|(d==1)|(gcd(d, n/d)!=1)|!harm(d))); t, 0)), n++); n)}
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CROSSREFS
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Cf. A001599 for harmonic numbers.
Adjacent sequences: A035524 A035525 A035526 this_sequence A035528 A035529 A035530
Sequence in context: A090898 A134872 A049603 this_sequence A085844 A083387 A104511
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KEYWORD
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nonn
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AUTHOR
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Jeff Burch (gburch(AT)erols.com)
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