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A080393 a(n) is the smallest integer such that A080383(a[n])=n. 0
0, 1, 2, 3, 40, 5, 12, 25, 1122, 13, 420, 1103 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

It is undecided whether all positive integers arise here or not.

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

a(1)=0; parity of n and a(n) is opposite; n=10: a(10)=13 because in A080383 10 appears first as 13th term; extension: a(14)=421

MATHEMATICA

f[x_] := Count[Table[IntegerQ[Binomial[x, Floor[x/2]]/ Binomial[x, j]], {j, 0, n}], True]; t=Table[0, {20}]; Do[s=f[n]; If[s<21&&t[[s]]==0, t[[s]]=n], {n, 1, 1300}]; t

CROSSREFS

Cf. A080383, A080385(1)=a(7), A080386(1)=a(8), A080387(1)=a(10), A080384(1)=a(6).

Sequence in context: A039820 A153745 A076724 * A111683 A323734 A088984

Adjacent sequences:  A080390 A080391 A080392 * A080394 A080395 A080396

KEYWORD

nonn

AUTHOR

Labos Elemer, Mar 17 2003

STATUS

approved

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Last modified March 20 05:17 EDT 2019. Contains 321344 sequences. (Running on oeis4.)