A264804 a(n) is least number > 0 such that the concatenation of a(1) ... a(n) is 11-gonal: (9n^2 - 7n)/2.

1, 1, 526, 64095, 21420730041, 4528059468080555555556, 3834345160635370971474665069772601398563211, 100751687713984558500838936986634939491022212000570658953744730444103042117925197608458

Offset

1,3

Links

Chai Wah Wu, Table of n, a(n) for n = 1..11

Wikipedia, Polygonal number

Prog

(PARI) hendecagonal(n)=ispolygonal(n, 11)
first(m)=my(v=vector(m), s=""); s="1"; print1(1, ", "); for(i=2, m, n=1; while(!hendecagonal(eval(concat(s, Str(n)))), n++); print1(n, ", "); s=concat(s, Str(n)))

Crossrefs

Cf. A051671, A051682 (11-gonal numbers), A061109, A061110, A261696, A264733, A264738, A264776, A264777, A264842, A264848, A264849.

Sequence in context: A251022 A251108 A204472 * A093226 A153660 A337779

Adjacent sequences: A264801 A264802 A264803 * A264805 A264806 A264807

Keyword

nonn,base

Author

Anders Hellström, Nov 25 2015

Extensions

a(5)-a(8) from Chai Wah Wu, Mar 16 2018

Status

approved