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A264738 a(n) is least number > 0 such that the concatenation of a(1) ... a(n) is triangular (m*(m+1)/2). 9
1, 5, 3, 181, 88028, 21235051740, 567915201450407862150, 344114043575504570099838908555592732193828, 2517587700386740093077985318903210991887701682095104296188806385635425261250603998340 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Jon E. Schoenfield, Table of n, a(n) for n = 1..12
PROG
(PARI) istriangular(n)=ispolygonal(n, 3)
first(m)=my(v=vector(m), s="1"); v[1]=1; for(i=2, m, n=1; while(!istriangular(eval(concat(s, Str(n)))), n++); v[i]=n; s=concat(s, Str(n))); v
CROSSREFS
Sequence in context: A267512 A230389 A048885 * A002208 A100653 A105318
KEYWORD
nonn,base
AUTHOR
Anders Hellström, Nov 22 2015
EXTENSIONS
a(6)-a(9) from Jon E. Schoenfield, Nov 22 2015
STATUS
approved

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Last modified March 3 16:27 EST 2024. Contains 370512 sequences. (Running on oeis4.)