The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A078613 Same numbers of distinct prime factors of forms 4*k+1 and 4*k+3. 6
 1, 2, 4, 8, 15, 16, 30, 32, 35, 39, 45, 51, 55, 60, 64, 70, 75, 78, 87, 90, 91, 95, 102, 110, 111, 115, 117, 119, 120, 123, 128, 135, 140, 143, 150, 153, 155, 156, 159, 174, 175, 180, 182, 183, 187, 190, 203, 204, 215, 219, 220, 222, 225, 230, 234, 235, 238, 240 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Equivalently, numbers n such that A005089(n)=A005091(n); a005094(a(n))=0. A001221(a(n)) and a(n) are of opposite parity. If m is in the sequence, then also 2*m. Conjecture : a(n) is asymptotic to c*n where c is around 4 - Benoit Cloitre, Jan 06 2003 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 EXAMPLE n = 99 = [(4*0+3)^2]*[(4*1+1)], therefore 99 is a term. MATHEMATICA fQ[n_]:=Plus@@((Mod[#[[1]], 4]-2)&/@If[n==1, {}, FactorInteger[n]])==0; Select[Range[240], fQ] (* Ray Chandler, Dec 18 2011*) PROG (Haskell) a078613 n = a078613_list !! (n-1) a078613_list = filter ((== 0) . a005094) [1..] -- Reinhard Zumkeller, Jan 07 2013 CROSSREFS Cf. A072202. Cf. A221264, A221265. Sequence in context: A084345 A084561 A277166 * A072202 A275474 A076351 Adjacent sequences:  A078610 A078611 A078612 * A078614 A078615 A078616 KEYWORD nonn AUTHOR Reinhard Zumkeller, Dec 10 2002 EXTENSIONS Edited by Ray Chandler, Dec 18 2011 STATUS approved

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

Last modified September 29 06:29 EDT 2020. Contains 337425 sequences. (Running on oeis4.)