A176717 Numbers n such that sum of digits of all distinct prime factors of n-th semiprime = sum of digits of all distinct prime factors of (n+1)-th semiprime.

13, 15, 16, 20, 79, 91, 111, 116, 117, 119, 125, 131, 205, 215, 225, 250, 276, 282, 284, 298, 303, 313, 332, 340, 362, 364, 446, 501, 523, 554, 562, 686, 720, 728, 759, 796, 798, 830, 877, 904, 923, 925, 953, 962, 978, 986, 988, 992, 1007, 1056, 1097, 1117

Offset

1,1

Links

Table of n, a(n) for n=1..52.

Example

a(1)=2 because 1st semiprime = 2*2 and 2=2; a(2)=5 because 2nd semiprime=2*3 and 2<3.

Maple

A007953 := proc(n) add(d, d=convert(n, base, 10)) ; end proc: A176707 := proc(n) local p; p := numtheory[factorset](A001358(n)) ; add( A007953(d), d=p) ; end proc: isA176717 := proc(n) A176707(n) = A176707(n+1) ; end proc: for n from 1 to 1200 do if isA176717(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Apr 26 2010

Crossrefs

Cf. A095402, A176707.

Sequence in context: A278978 A212908 A180642 * A070603 A329183 A302440

Adjacent sequences: A176714 A176715 A176716 * A176718 A176719 A176720

Keyword

nonn,base

Author

Juri-Stepan Gerasimov, Apr 24 2010

Extensions

Corrected (13 inserted, 20 inserted, 34 and 55 removed) and extended beyond 91 by R. J. Mathar, Apr 26 2010

Status

approved