OFFSET
0,1
LINKS
Robert Israel, Table of n, a(n) for n = 0..632
FORMULA
a(n) = ceiling(sqrt(4*A002110(n))). - Michel Marcus, Feb 22 2016
MAPLE
P:= 1: p:= 1: A[0]:= 2:
for n from 1 to 30 do
p:= nextprime(p);
P:= P*p;
A[n]:= ceil(sqrt(4*P));
od:
seq(A[i], i=0..30); # Robert Israel, Mar 18 2020
MATHEMATICA
p=4; Join[{Sqrt[p]}, Table[p=p*Prime[n]; Ceiling[Sqrt[p]], {n, 25}]]
PROG
(PARI) a(n) = sqrtint(4*prod(k=1, n, prime(k)) - 1) + 1; \\ Michel Marcus, Feb 22 2016; corrected Jun 16 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Nov 23 2010
EXTENSIONS
Extended by T. D. Noe, Nov 23 2010
STATUS
approved