OFFSET
1,1
COMMENTS
Terms at the end of each run, that is, terms k that are not followed by k+1 (i.e., this excludes terms like 95, 147, 209, 901 .. 905, 1149, ...) form a subsequence of A181062. - Antti Karttunen, Jan 20 2020
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..210 (terms 1..72 from Chai Wah Wu)
Christophe Soulé, Le triangle de Pascal et ses propriétés, Lecture, Soc. Math. de France, Feb 13 2008.
MAPLE
A276781 := proc(n)
local b, k;
for b from 0 to floor(n/2+1) do
igcd(seq(binomial(n, k), k=b..n-b)) ;
if % > 1 then
return b ;
end if;
end do:
end proc:
am := -1 ;
for n from 2 do
an := A276781(n) ;
if an > am then
printf("%d, \n", n) ;
am := an ;
end if;
end do: # R. J. Mathar, Sep 30 2016
MATHEMATICA
Function[t, First@ Position[t, #] & /@ Range@ Max@ t][{0}~Join~Table[b = 1; While[GCD @@ Map[Binomial[n, #] &, Range[b, n - b]] == 1, b++]; b, {n, 2, 1500}]] // Flatten (* Michael De Vlieger, Oct 03 2016 *)
PROG
(PARI)
A276781(n) = if(1==n, 1, forstep(k=n, 1, -1, if(isprimepower(k), return(1+n-k))));
m=0; k=0; n=1; while(k<210, n++; if((t=A276781(n))>m, m=t; k++; print1(n, ", "))); \\ Antti Karttunen, Jan 29 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 29 2016
EXTENSIONS
a(11)-a(30) from R. J. Mathar, Sep 30 2016
More terms from Chai Wah Wu, Oct 02 2016
Definition amended because of the changed definition of A276781, while keeping the terms same as before. - Antti Karttunen, Jan 29 2020
STATUS
approved