A241540 Indices of primes p in A182514, i.e., a(n) = primepi(p) = A000720(A182514(n)).
1, 2, 4, 30, 217, 49749629143526
Offset: 1
This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
3 is the smallest prime followed by 1 composite number, 7 is the smallest prime followed by 2 or more composite numbers, 23 is the smallest prime followed by 4 or more composite numbers, 113 is the smallest prime followed by 8 or more composite numbers.
Table[p = 2; While[NextPrime@ p - p <= 2^n, p = NextPrime@ p]; p, {n, 0, 7}] (* Michael De Vlieger, Jan 27 2016 *)
a(n) = {my(p = 2); while(((q=nextprime(p+1)) - p) < 2^n+1, p = q); p;} \\ Michel Marcus, Jan 27 2016
from sympy import isprime def A268140(n): p, n2 = 2, 2**n+1 while True: for i in range(1,n2): if isprime(p+i): p += i break else: return p # Chai Wah Wu, Feb 15 2016
Comments