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 A279952 Number of primes with prime subscripts dividing n. 6
 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 2, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 0, 0, 2, 1, 0, 2, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 2, 0, 0, 1, 0, 1, 2, 0, 0, 1, 2, 0, 1, 0, 1, 2, 0, 1, 1, 0, 1, 2, 1, 1, 1, 1, 0, 1, 0, 0, 2, 0, 1, 1, 0, 1, 1, 1, 1, 1, 2, 0, 1, 1, 0, 2, 0, 0, 2, 0, 1, 1, 0, 0, 2, 1, 0, 2, 0, 0, 2, 0, 0, 1, 1, 2, 1, 0, 0, 1, 1, 0, 1, 1, 1, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,15 LINKS G. C. Greubel, Table of n, a(n) for n = 1..5000 FORMULA G.f.: Sum_{k>=1} x^prime(prime(k))/(1 - x^prime(prime(k))). EXAMPLE a(15) = 2 because 15 has 4 divisors {1,3,5,15} among which 2 divisors {3,5} are primes with prime subscripts. MATHEMATICA Rest[nmax = 120; CoefficientList[Series[Sum[x^Prime[Prime[k]]/(1 - x^Prime[Prime[k]]), {k, 1, nmax}], {x, 0, nmax}], x]] PROG (PARI) x='x+O('x^120); concat([0, 0], Vec(sum(k=1, 120, x^prime(prime(k))/(1 - x^prime(prime(k)))))) \\ Indranil Ghosh, May 23 2017 CROSSREFS Cf. A001221, A006450. Sequence in context: A353918 A305490 A113706 * A054845 A317991 A359980 Adjacent sequences: A279949 A279950 A279951 * A279953 A279954 A279955 KEYWORD nonn,easy AUTHOR Ilya Gutkovskiy, Dec 23 2016 STATUS approved

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Last modified June 8 02:04 EDT 2023. Contains 363157 sequences. (Running on oeis4.)