A161183 Terms which occur at least twice in A161182.

1, 9, 16, 25, 53, 78, 82, 89, 115, 120, 130, 152, 161, 178, 196, 224, 233, 235, 250, 256, 265, 286, 291, 300, 301, 314, 315, 325, 347, 357, 360, 368, 381, 391, 397, 419, 428, 430, 456, 468, 479, 483, 484, 494, 495, 512, 528, 570, 577, 589, 591, 608, 610, 620

Offset: 1

Author

Daniel Tisdale, Jun 05 2009

Keywords

• easy
• nonn

Comments

A161182 is not monotonic, so some terms (like 89) listed here are not direct neighbors in A161182. - R. J. Mathar, Jun 22 2009

Crossrefs

Cf. A078435, A161182.

Programs

Maple

A038107 := proc(n) numtheory[pi]( n^2) ; end: A078435 := proc(n) n^2-A038107(n) ; end: A161182 := proc(n) A078435(n)-A078435(n-1) ; end: L := [] ; for n from 1 to 1200 do L := [op(L), A161182(n)] ; od: read("transforms3") ; L := sort(L) ; L := LISTDUPL(L,0) ; # R. J. Mathar, Jun 22 2009

Mathematica

f[n_] := 2n - 1 - PrimePi[n^2] + PrimePi[(n-1)^2];
Select[Split[Array[f, 1000]//Sort], Length[#] >= 2&][[All, 1]]
(* Jean-François Alcover, Mar 07 2023 *)

Extensions

Edited by N. J. A. Sloane, Jun 07 2009

Missing numbers added by R. J. Mathar, Jun 22 2009