OFFSET
2,1
COMMENTS
The sequence has the same records as A002618.
LINKS
Antti Karttunen, Table of n, a(n) for n = 2..16385
FORMULA
MAPLE
A174857 := proc(n) local k, aref ; aref := A020639(n) ; for k from 1 do if A020639(n+k) = aref then return k; end if; end do: end proc:
seq(A174857(n), n=2..80) ; # R. J. Mathar, Dec 07 2010
MATHEMATICA
Block[{s = Array[FactorInteger[#][[1, 1]] &, 10^4]}, Array[If[EvenQ[#], 2, Block[{k = 1, n = s[[#]]}, While[n != s[[# + k]], k++; If[# + k > Length[s], AppendTo[s, FactorInteger[# + k][[1, 1]] ]] ]; k]] &, 78, 2]] (* Michael De Vlieger, Apr 06 2021 *)
PROG
(PARI)
A020639(n) = if(1==n, n, factor(n)[1, 1]);
A174857(n) = if(isprime(n), (n-1)*n, my(spf=A020639(n)); for(k=1, oo, if(A020639(n+k)==spf, return(k)))); \\ Antti Karttunen, Apr 06 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Mar 31 2010
STATUS
approved