The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A213420 Smallest number k such that the sum of prime factors of k (counted with multiplicity) is n times a square > 1. 3
 4, 15, 35, 39, 51, 95, 115, 87, 155, 111, 123, 215, 235, 159, 371, 183, 302, 335, 219, 511, 395, 415, 267, 623, 291, 303, 482, 327, 339, 791, 554, 1415, 635, 655, 411, 695, 662, 447, 698, 471, 734, 815, 835, 519, 1211, 543, 842, 1991, 579, 591, 914, 2167, 2587 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Smallest k such that sopfr(k) = n*q^2. a(n) = A213386(n), except for n = 1, 105, 173, 213, 227, 287, … LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE a(105) = 3764 because 3764 = 2^2 * 941 and the sum of prime factors (counted with multiplicity) is 4 + 941 = 945 = 105*9 where 9 is a square. MAPLE with(numtheory): sopfr:= proc(n) option remember; add(i[1]*i[2], i=ifactors(n)[2]) end: a:= proc(n) local k, p; for k from 2 while irem(sopfr(k), n, 'p')>0 or sqrt(p)<>floor(sqrt(p)) or p=1 do od; k end: seq (a(n), n=1..100); CROSSREFS Cf. A213386, A212401. Sequence in context: A054556 A113693 A211537 * A209345 A323452 A330204 Adjacent sequences: A213417 A213418 A213419 * A213421 A213422 A213423 KEYWORD nonn AUTHOR Michel Lagneau, Jun 11 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 14 06:54 EDT 2024. Contains 375920 sequences. (Running on oeis4.)