A169640 Numbers n such that sum of digits of the n-th prime = the sum of digits of the n-th semiprime.

23, 31, 38, 52, 54, 62, 84, 93, 98, 111, 118, 135, 150, 201, 209, 215, 228, 258, 266, 288, 299, 330, 348, 352, 379, 399, 400, 471, 476, 479, 488, 500, 509, 511, 533, 538, 540, 545, 560, 585, 598, 618, 624, 629, 678, 693, 714, 720, 751, 752, 759, 771, 790, 805

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

A007605(a(n))=A175013(a(n)).

A007953(A000040(n)) = A007953(A001358(n)). - Chandler

Example

a(1)=23 because 23rd prime=83(8+3=11) and 23rd semiprime=65(6+5=11).

Mathematica

Module[{nn=900, sps}, sps=Take[Select[Range[4nn], PrimeOmega[#]==2&], nn]; Position[Thread[{Prime[Range[nn]], sps}], _?(Total[IntegerDigits[#[[1]]]] == Total[IntegerDigits[#[[2]]]]&), 1, Heads->False]]//Flatten (* Harvey P. Dale, Oct 09 2017 *)

Crossrefs

Cf. A007605, A175013.

Sequence in context: A155107 A126719 A110677 * A026051 A141818 A060328

Adjacent sequences: A169637 A169638 A169639 * A169641 A169642 A169643

Keyword

nonn,base,less

Author

Juri-Stepan Gerasimov, Apr 04 2010

Extensions

Edited by N. J. A. Sloane, Apr 05 2010

Edited, corrected and extended by Ray Chandler, Apr 05 2010

Status

approved