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A075000 Smallest number such that n*a(n) is a concatenation of n consecutive integers; or 0 if no such number exists. 13

%I #17 Feb 09 2018 21:48:10

%S 1,6,41,864,2469,20576,493827,7098637639,13717421,1234567891,

%T 82737383012865106529,10288065758426,3513762316247164732,

%U 563643651522439401227280,8230452606740808761

%N Smallest number such that n*a(n) is a concatenation of n consecutive integers; or 0 if no such number exists.

%C Conjecture: For every n there exists a nonzero a(n).

%H Robert G. Wilson v, <a href="/A075000/b075000.txt">Table of n, a(n) for n = 1..100</a>

%F a(n) = A077306(n)/n. - _Amarnath Murthy_, Nov 03 2002

%e a(11) = 82737383012865106529 as 11*82737383012865106529 = 910111213141516171819 is the concatenation of 11 numbers from 9 to 19.

%t f[ n_ ] := Block[ {id = Range@n}, While[ k = FromDigits@ Flatten@ IntegerDigits@ id/n; !IntegerQ@k, id++ ]; k ]; Array[ f, 16 ] (* _Robert G. Wilson v_, Oct 19 2007 *)

%Y Cf. A074991, A074992, A074993, A074994, A074995, A074996, A036377, A073086, A074999, A075001.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Aug 31 2002

%E More terms from _Rick L. Shepherd_, Sep 03 2002

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Last modified April 18 22:18 EDT 2024. Contains 371782 sequences. (Running on oeis4.)