cp's OEIS Frontend

A076069 Largest number formed as concatenation of a permutation of the n consecutive numbers 1+n(n-1)/2, ..., n(n+1)/2 (written in decimal).

%I A076069 #9 Mar 31 2012 13:48:30
%S A076069 1,32,654,98710,1514131211,212019181716,28272625242322,
%T A076069 3635343332313029,454443424140393837,55545352515049484746,
%U A076069 6665646362616059585756,787776757473727170696867,91908988878685848382818079,9998979695949392105104103102101100
%N A076069 Largest number formed as concatenation of a permutation of the n consecutive numbers 1+n(n-1)/2, ..., n(n+1)/2 (written in decimal).
%C A076069 Nontrivial (i.e., different from concatenation in reverse order) whenever a number of the form 10^k is in the considered range of n numbers; then a(n) is given as concatenation (10^k-1)...(1+n(n-1)/2)(n(n+1)/2)...(10^k).
%e A076069 1, then a concatenation of a permutation of 2 and 3, then a concatenation of a permutation of 4, 5 and 6.
%o A076069 (PARI 2.4.2) a(n)=eval(concat(vecsort(vector(n, i, Str(i+n*(n-1)/2)),,4)))
%Y A076069 Cf. A076068, A080479, A080480, A192392.
%K A076069 nonn,easy,less,base
%O A076069 1,2
%A A076069 _M. F. Hasler_, Jun 29 2011
%E A076069 Definition modified to obtain a new sequence different from (earlier duplicate) A080480. M. F. Hasler, Jun 29 2011.