

A077693


Smallest triangular number which begins with the concatenation of n times digits of n.


2



1, 2211, 333336, 4444671, 5555581345, 666666622350, 777777723060715, 88888888106421690, 9999999993293677081, 101010101010101010104859338144028152581, 1111111111111111111111683873730855571564421
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OFFSET

1,2


COMMENTS

21, 2211, 222111, 22221111, ...and 6, 561, 55611, 5556111, 555561111 give patterned triangular number sequences of patterned number sequences 6, 66, 666, ... and 3, 33, 333, ...respectively. Are there any other patterns?


LINKS

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


EXAMPLE

a(4) = 4444671 begins with 4444.


PROG

(PARI) {rT(m) = ceil((sqrt(8*m+1)1)/2)} {len10(m) = ceil(log(m+1)/log(10))} {T(n) = (n*(n+1))/2} for(n=1, 20, l=len10(n); m=n*(10^(l*n)1)/(10^l1); for(k=0, 10^6, t=rT(m*10^k); if(T(t)<(m+1)*10^k, print1(" ", T(t)); break))) (Alekseyev)


CROSSREFS

Cf. A077692.
Sequence in context: A191679 A238456 A031725 * A253735 A259892 A337160
Adjacent sequences: A077690 A077691 A077692 * A077694 A077695 A077696


KEYWORD

base,nonn


AUTHOR

Amarnath Murthy, Nov 18 2002


EXTENSIONS

Corrected and extended by Max Alekseyev, Feb 15 2005


STATUS

approved



