

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
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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: A232928 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



