login
Partial sums of skinny numbers (A061909).
1

%I #7 Aug 02 2017 14:00:51

%S 1,3,6,16,27,39,52,72,93,115,145,176,276,377,479,582,692,803,915,1028,

%T 1148,1269,1391,1521,1721,1922,2124,2334,2545,2757,2977,3198,3498,

%U 3799,4109,4420,5420,6421,7423,8426,9436,10447,11459,12472,13492,14513,15535

%N Partial sums of skinny numbers (A061909).

%C The skinny partial sums of skinny numbers begin: a(1) = 1, a(2) = 3. The primes in the sequence begin: a(2) = 3, a(15) = 479, a(15) = 1721, a(38) = 6421, a(52) = 20899. The perfect powers in the sequence begin a(4) = 16 = 2^4, a(5) = 27 = 3^3, a(24) = 1521 = 39^2.

%H Harvey P. Dale, <a href="/A130596/b130596.txt">Table of n, a(n) for n = 1..1000</a>

%e a(36) = 4420 = 1+2+3+10+11+12+13+20+21+22+30+31+100+101+102+103+110+111+112+113+120+121+122+130+200+201+202+210+211+212+220+221+300+301+310+311

%t Accumulate[Select[Range[0,1200],IntegerReverse[#^2]==IntegerReverse[#]^2&]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Aug 02 2017 *)

%K base,easy,nonn

%O 1,2

%A _Jonathan Vos Post_, Jun 17 2007