%I A094609
%S A094609 4,7,49,52,295,369,415,499,502,594,652,760,2254,4999,5002,8827,10330,
%T A094609 14877,49999,50002,490150,499999,500002,509949,3347109,4999999,5000002,
%U A094609 6983470,24913494,49999999,50000002
%N A094609 Numbers n such that n concatenated with n+1 is triangular.
%C A094609 Numbers 4, 49, 499, 4999, ...; 52, 502, 5002, 50002, ...; 594, 509949, 
               500999499, 500099994999, ...; 415, 490150, 499001500, 499900015000, 
               ...; with obvious patterns are members of the sequence. - Vladeta 
               Jovovic (vladeta(AT)eunet.rs), Jun 09 2004
%e A094609 E.g. 5253 is triangular so 52 is a member.
%t A094609 triQ[n_] := Block[{k = Floor[ Sqrt[2n]]}, If[ k(k + 1) == 2n, True, False]]; 
               Do[ If[ triQ[ FromDigits[ Join[ IntegerDigits[n], IntegerDigits[n 
               + 1]] ]] == True, Print[ n]], {n, 45000000}] (from Robert G. Wilson 
               v Jun 09 2004)
%Y A094609 Cf. A000217.
%Y A094609 Sequence in context: A093102 A139030 A115439 this_sequence A049191 A013467 
               A060413
%Y A094609 Adjacent sequences: A094606 A094607 A094608 this_sequence A094610 A094611 
               A094612
%K A094609 base,nonn
%O A094609 1,1
%A A094609 Jason Earls (zevi_35711(AT)yahoo.com), Jun 06 2004
%E A094609 More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 09 2004