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%I #6 Mar 12 2022 14:09:32
%S 1,3,2,13,4,5,6,7,8,9,10,11,12,183,14,15,16,17,18,19,20,21,22,23,24,
%T 25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,
%U 48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71
%N a(n) is the smallest number which is not the sum of exactly 1 or of n earlier terms.
%F If n-1 > 0 has not already appeared in sequence then a(n) = n-1, otherwise a(n) = n^2 - n + 1.
%e a(3)=2 because 1 is already in the sequence, 2 has not yet appeared (i.e., is not the sum of 1 earlier term), and the sum of 3 earlier terms is 3, 5 or 7.
%e a(4)=13 because 1, 2, and 3 have already appeared and the sum of 4 earlier terms could be any integer from 4 through 12.
%Y Cf. A035334. a(n) is not n-1 iff n-1 is in A024556 or equivalently in A002065.
%K easy,nonn
%O 1,2
%A _Henry Bottomley_, May 19 2000
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