A077695 - OEIS

%I #9 Oct 15 2021 17:08:19

%S 1,253,55611,9876790,1543206790,222222111111,30246911419753,

%T 3950617249382716,499999999500000000,

%U 51015202530354045509590858075706560555,617283950617283950617716049382716049382716

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

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

%H Harvey P. Dale, <a href="/A077695/b077695.txt">Table of n, a(n) for n = 1..166</a>

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

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

%Y Cf. A077692, A077693, A077694, A000461.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Nov 18 2002

%E More terms from _Sascha Kurz_, Jan 07 2003