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A099467 a(1) = a(2) = 1; for n > 2, a(n) is the smallest number > a(n-1) which is not the sum of 2 consecutive elements of the sequence. 3
1, 1, 3, 5, 6, 7, 9, 10, 12, 14, 15, 17, 18, 20, 21, 23, 24, 25, 27, 28, 30, 31, 33, 34, 36, 37, 39, 40, 42, 43, 45, 46, 48, 50, 51, 53, 54, 56, 57, 59, 60, 62, 63, 65, 66, 68, 69, 71, 72, 74, 75, 77, 78, 80, 81, 83, 84, 86, 87, 89, 90, 92, 93, 95, 96, 97 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

The first differences are 1 and 2 strictly alternately, except near powers of 2: a(2^k+2)-a(2^k+1) = a(2^k+1)-a(2^k). Cf. A001651 which is generated by the same rule if we start from 1, 2 and has first differences 1, 2, 1, 2... with no exceptions. - Andrey Zabolotskiy, Feb 11 2021

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

A[1]:= 1: A[2]:= 1: forbid:= {2}:

for n from 3 to 100 do

for k from A[n-1]+1 while member(k, forbid) do od:

A[n]:= k;

forbid:= forbid union {A[n-1]+k};

od:

seq(A[i], i=1..100); # Robert Israel, Nov 29 2017

CROSSREFS

Cf. A022442 (complement), A001651.

Sequence in context: A137624 A238246 A330998 * A054353 A284555 A031948

Adjacent sequences: A099464 A099465 A099466 * A099468 A099469 A099470

KEYWORD

easy,nonn

AUTHOR

Gaetan Polard (gaetan27(AT)hotmail.com), Nov 18 2004

STATUS

approved

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Last modified January 29 17:53 EST 2023. Contains 359925 sequences. (Running on oeis4.)