A319500 a(n) is the least m for which A006987(n) = binomial(m,k) for some k, 2 <= k <= m/2.

4, 5, 6, 6, 7, 8, 7, 9, 10, 11, 8, 12, 8, 13, 9, 14, 15, 10, 9, 17, 18, 11, 19, 20, 10, 12, 22, 10, 23, 24, 13, 25, 26, 11, 27, 14, 28, 29, 30, 15, 11, 31, 12, 32, 33, 16, 34, 35, 36, 37, 17, 38, 13, 39, 40, 12, 18, 41, 42, 43, 12, 44, 19, 45, 14, 46, 47, 48, 20, 49, 50, 51, 13, 52, 21, 15, 53

Offset

1,1

Comments

First differs from A022911 at n=18.

Links

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

Formula

A006987(n) = binomial(a(n),A318955(n)).

Example

a(3) = 6 because A006987(3) = 15 = binomial(6,2).

Maple

N:= 10000: # for binomial(n, k) values <= N
S:= {}:
for n from 2 while n*(n-1)/2 <= N do
  for k from 2 to n/2 do
    v:= binomial(n, k);
    if v > N then break fi;
    if not member(v, S) then
      S:= S union {v};
      M[v]:= n;
    fi
od od:
A006987:= sort(convert(S, list)):
seq(M[A006987[i]], i=1..nops(A006987));

Crossrefs

Cf. A006987, A022911, A318955.

Sequence in context: A225491 A046343 A273227 * A022911 A162310 A116962

Adjacent sequences: A319497 A319498 A319499 * A319501 A319502 A319503

Keyword

nonn

Author

Robert Israel, Sep 20 2018

Status

approved