OFFSET
1,1
LINKS
Daniel Suteu, Table of n, a(n) for n = 1..500
EXAMPLE
a(4)=67=A000040(19): 2*67+1 = 135 = 5*3^3, 4 factors.
PROG
(PARI)
generate(A, B, n) = A=max(A, 2^n); (f(m, p, n) = my(list=List()); if(n==1, forprime(q=max(p, ceil(A/m)), B\m, my(t=m*q); if(isprime((t-1)/2), listput(list, (t-1)/2))), forprime(q = p, sqrtnint(B\m, n), my(t=m*q); list=concat(list, f(t, q, n-1)))); list); vecsort(Vec(f(1, 3, n)));
a(n) = my(x=2^n, y=2*x); while(1, my(v=generate(x, y, n)); if(#v >= 1, return(v[1])); x=y+1; y=2*x); \\ Daniel Suteu, Feb 05 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jun 11 2002
EXTENSIONS
More terms from Don Reble, Apr 15 2003
STATUS
approved