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A126196
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Numbers n such that gcd(numerator(H(n)),numerator(H([n/2]))) > 1, where H() are the harmonic numbers.
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13
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OFFSET
| 1,1
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COMMENTS
| Note a connection to the Wieferich primes A001220(n) = {1093, 3511} = primes p such that p^2 divides 2^(p-1) - 1. a(3) = 1093 - 1. a(4) = (3511- 1)/2. a(5) = 3511 - 1.
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CROSSREFS
| Cf. A126197, A001008 and A125581.
Cf. A125581 = numbers n such that n does not divide the denominator of the n-th harmonic number nor the denominator of the n-th alternating harmonic number. Cf. A126197 = GCD's arising in A126196. Cf. A001220 = Wieferich primes p: p^2 divides 2^(p-1) - 1. Cf. A001008, A002805 = Denominator of the n-th harmonic number. Cf. A058313, A058312 = Denominator of the n-th alternating harmonic number. Cf. A074791 = numbers n such that n does not divide the denominator of the n-th harmonic number. Cf. A121594 = numbers n such that n does not divide the denominator of the n-th alternating harmonic number.
Sequence in context: A003396 A124899 A056852 * A093169 A159029 A068616
Adjacent sequences: A126193 A126194 A126195 * A126197 A126198 A126199
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KEYWORD
| nonn
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AUTHOR
| Max Alekseyev and Tanya Khovanova, Mar 07 2007, corrected Mar 10 2007
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