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 A097975 a(n) is the prime divisor of n which is >= sqrt(n), or 0 if there is no such prime divisor. 2
 0, 2, 3, 2, 5, 3, 7, 0, 3, 5, 11, 0, 13, 7, 5, 0, 17, 0, 19, 5, 7, 11, 23, 0, 5, 13, 0, 7, 29, 0, 31, 0, 11, 17, 7, 0, 37, 19, 13, 0, 41, 7, 43, 11, 0, 23, 47, 0, 7, 0, 17, 13, 53, 0, 11, 0, 19, 29, 59, 0, 61, 31, 0, 0, 13, 11, 67, 17, 23, 0, 71, 0, 73, 37, 0, 19, 11, 13, 79, 0, 0, 41, 83 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Sequence also is the sum of distinct prime divisors of n which are >= sqrt(n). At most one prime divisor of n is >= square root of n. LINKS Diana Mecum, Table of n, a(n) for n = 1..1000 MATHEMATICA Do[l = Select[Select[Divisors[n], PrimeQ], # >= Sqrt[n]&]; If[Length[l] == 0, Print[0], Print[l[[1]]]], {n, 1, 50}] (* Ryan Propper, Jul 24 2005 *) Array[Select[FactorInteger[#][[All, 1]], Function[p, p >= Sqrt@ #]] /. {{} -> {0}, {1} -> {0}} &, 83][[All, 1]] (* Michael De Vlieger, Dec 22 2017 *) PROG (PARI) a(n) = sumdiv(n, d, if (isprime(d) && (d^2 >= n), d)); \\ Michel Marcus, Dec 23 2017 CROSSREFS Cf. A097974. Sequence in context: A323021 A026235 A086281 * A130088 A078834 A039634 Adjacent sequences:  A097972 A097973 A097974 * A097976 A097977 A097978 KEYWORD nonn AUTHOR Leroy Quet, Sep 07 2004 EXTENSIONS More terms from Ryan Propper, Jul 24 2005 More terms from Stefan Steinerberger, Jan 21 2006 Further terms from Diana L. Mecum, Jun 15 2007 STATUS approved

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Last modified January 15 18:55 EST 2021. Contains 340188 sequences. (Running on oeis4.)