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 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 (list; graph; refs; listen; history; text; internal format)
 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 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^l-1); 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

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Last modified December 8 11:31 EST 2021. Contains 349596 sequences. (Running on oeis4.)