A088982 -id:A088982 - cp's OEIS frontend

A175249 Noncomposites (A008578) with nonprime (A018252) subscripts.

1, 5, 11, 17, 19, 23, 31, 41, 43, 47, 59, 67, 71, 73, 83, 89, 97, 101, 103, 109, 127, 131, 137, 139, 149, 157, 163, 167, 179, 191, 193, 197, 211, 223, 227, 229, 233, 241, 251, 257, 263, 269, 277, 283, 293, 307, 311, 313, 331, 337, 347, 353, 367, 373, 379, 383, 389, 401, 409, 419

Offset: 1

Jaroslav Krizek, Mar 13 2010

nonn

			a(5) = 19 because a(5) = q(b(5)) = q(9) = 19, q = noncomposite, b = nonprime.

Cf. A008578, A018252, A088982.

Join[{1}, Table[Prime[ResourceFunction["Composite"][n] - 1], {n, 1, 100}]]

a(n) = noncomposite(nonprime(n)) = A008578(A018252(n)).

a(34)-a(60) from Terry D. Grant, Aug 16 2016

A309649 Sieved recursive primeth recurrence (see Comments for precise definition).

Original entry on oeis.org

1, 7, 13, 19, 23, 29, 37, 43, 47, 53, 61, 71, 73, 79, 89, 97, 101, 103, 107, 113, 131, 137, 139, 149, 151, 163, 167, 173, 181, 193, 197, 199, 223, 227, 229, 233, 239, 251, 257, 263

Offset: 1

Eduard Baumann, Aug 17 2019

This is a sieve constructed on the baise of A007097 (the "primeth recurrence"). Delete the elements of A007097 in the list of the prime numbers and take the smallest remaining prime and call it a(2). Start a new primeth recurrence series with a(2) as starting element instead of 1. Take b(1) to be a(2), then b(2) is the b(1)-th prime, then b(3) is the b(2)-th prime and so on. Delete also the numbers b(i) of this new sequence from the primes. Again take the smallest remaining prime and callit a(3). Start a new primeth recurrence series with this number a(3) as starting element. Continue this process and retain all smallest elements 1, a(2), a(3), a(4), ... The resulting sequence is 1, 7, 13, 19, 23, 29, 37, 43, 47, 53, 61, 71, 73, 79, 89, 97, 101, 103, 107, 113, 131, 137, 139, 149, 151, 163, 167, 173, 181, 193, 197, 199, 223, 227, 229, 233, 239, 251, 257, 263, ...

Appears to be essentially the same as A088982 and A007821. - R. J. Mathar, Aug 22 2019

			First term a(1)=1.
For the 2nd term: take all primes and delete the primes from the sequence A007097 : 1,2,3,5,11,31,127, ..
This gives: 7,13,17,19, .. (1)
The smallest term is 7. Our a(2)=7.
Now construct an A007097 series with the starting term 7 instead of 1.
The 7th prime is 17. The 17th prime is 59. the 59th prime is 277. The numbers to delete from series (1) are 7,17,59,277 ..
This gives: 13,19,23,29,..  (2)
The smallest term now is 13. Our a(3)=13.
The next A007097 like series starting with 13 is the following.
13,41,179,.. which we delete from (2).
This gives: 19,23,29,..  (3)
The smallest term now is 19. Our a(4)=19.
And so on.

Cf. A007097.

A275991 a(n) = prime(composite(n)) - prime(n).

Original entry on oeis.org

5, 10, 14, 16, 18, 24, 26, 28, 30, 32, 40, 36, 38, 46, 50, 48, 44, 46, 46, 60, 64, 60, 66, 62, 66, 66, 70, 74, 84, 84, 72, 92, 90, 90, 84, 88, 94, 94, 96, 96, 92, 100, 102, 114, 114, 114, 106, 114, 120, 120, 126, 134, 138, 132, 132, 134, 140, 148, 144, 152, 156, 150

Offset: 1

Terry D. Grant, Aug 15 2016

			For n=3, prime(composite(3)) = 19, and prime(3) = 5, therefore a(3) = 19 - 5 = 14.

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Cf. A088982.

Module[{nn=100,cmps},cmps=Select[Range[nn],CompositeQ];Prime[cmps]-Prime[Range[Length[cmps]]]] (* Harvey P. Dale, Sep 02 2025 *)

a(n) = A000040(A002808(n)) - A000040(n) = A088982(n) - A000040(n).

Previous Mathematica program replaced by Harvey P. Dale, Sep 02 2025

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A175249 Noncomposites (A008578) with nonprime (A018252) subscripts.

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A309649 Sieved recursive primeth recurrence (see Comments for precise definition).

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A275991 a(n) = prime(composite(n)) - prime(n).

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