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A108853 Indices of prime Knuth numbers; that is, integers n such that the n-th Knuth number is prime. Indices of primes in A007448. 1
1, 2, 4, 5, 6, 10, 11, 12, 15, 16, 17, 18, 28, 29, 30, 40, 41, 42, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 121, 122, 123, 124, 125, 126, 136, 137, 138, 159, 160, 161, 162, 190, 191, 192, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Michael S. Branicky, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Knuth Number.

EXAMPLE

10 is a term because the 10th Knuth number, 13, is prime.

PROG

(Python)

from sympy import isprime, primepi

from itertools import count, islice

def agen():

A007448n, A007448lst = 1, [1]

for n in count(0):

if isprime(A007448n):

yield n

A007448n = 1 + min(2*A007448lst[n//2], 3*A007448lst[n//3])

A007448lst.append(A007448n)

print(list(islice(agen(), 61))) # Michael S. Branicky, Jul 15 2022

CROSSREFS

Cf. A007448.

Sequence in context: A140779 A348937 A117890 * A257085 A334736 A265349

Adjacent sequences: A108850 A108851 A108852 * A108854 A108855 A108856

KEYWORD

easy,nonn

AUTHOR

Ryan Propper, Jul 11 2005

EXTENSIONS

Extended by Ray Chandler, Jul 24 2005

STATUS

approved

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Last modified January 29 17:53 EST 2023. Contains 359925 sequences. (Running on oeis4.)