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A264738
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a(n) is least number > 0 such that the concatenation of a(1) ... a(n) is triangular (m*(m+1)/2).
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9
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1, 5, 3, 181, 88028, 21235051740, 567915201450407862150, 344114043575504570099838908555592732193828, 2517587700386740093077985318903210991887701682095104296188806385635425261250603998340
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OFFSET
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1,2
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LINKS
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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