A077695 - OEIS

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A077695

a(n) = triangular number pertaining to the number f(n) obtained by concatenating n n times.

1, 253, 55611, 9876790, 1543206790, 222222111111, 30246911419753, 3950617249382716, 499999999500000000, 51015202530354045509590858075706560555, 617283950617283950617716049382716049382716

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OFFSET

1,2

COMMENTS

a(n) = triangular number corresponding to A000461(n).

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..166

EXAMPLE

a(4) = 9876790 = 4444*4445/2.

MATHEMATICA

(#(#+1))/2&/@Table[FromDigits[Flatten[IntegerDigits/@PadRight[{}, n, n]]], {n, 15}] (* Harvey P. Dale, Oct 15 2021 *)

CROSSREFS