A048457 -id:A048457 - cp's OEIS frontend

A048458 'Prime last odd terms' from generation 2 onwards.

7, 23, 67, 179, 1109, 17427659, 1586875049, 7021048691, 1104052140838673681, 80729882077782801781, 49474191359283212247841, 152695677551802424534973144788818335406948326813, 50258816309715893690860594601285860231033059311672877749

Offset: 1

Patrick De Geest, May 15 1999

Intersection of A000040 and A048457.

Nathaniel Johnston, Table of n, a(n) for n = 1..20

For "Generations" see A048448-A048455. Cf. A048459. See also A047844.

a(9) - a(13) from Nathaniel Johnston, Apr 11 2011

A354430 First diagonal of an array, generated from the sequence of the nonprimes.

Original entry on oeis.org

1, 7, 22, 58, 142, 334, 766, 1726, 3837, 8435, 18364, 39646, 84986, 181117, 384160, 811676, 1709425, 3590213, 7522354, 15728427, 32827027, 68405533, 142344708, 295824870, 614046159, 1273068141, 2636250146, 5452584131, 11264148401, 23242423457, 47903544728

Offset: 1

Tamas Sandor Nagy, May 27 2022

Mirroring the idea in A048457, here with nonprimes, and including 1 of the first generation.

We write down the sequence of the nonprimes 1, 4, 6, ... in the first row of the array. Nonprime(k) + nonprime(k+2) will generate the second row. Thereafter we generate the further rows in a similar manner. The leftmost diagonal gives the sequence.

			1    4    6    8    9   10   12   14   15   16   18   20   21 ...
     7   12   15   18   21   24   27   30   33   36   39 ...
         22   30   36   42   48   54   60   66   72 ...
              58   72   84   96  108  120  132 ...
                  142  168  192  216  240 ...
                       334  384  432 ...
                            766 ...

Michael S. Branicky, Table of n, a(n) for n = 1..3311

Cf. A001787, A018252, A048457, A048448, A099862.

from sympy import composite
from functools import lru_cache
@lru_cache(maxsize=None)
def T(r, k):
    if r == 1: return 1 if k == 1 else composite(k-1)
    return T(r-1, k) + T(r-1, k+2)
def a(n): return T(n, 1)
print([a(n) for n in range(1, 30)]) # Michael S. Branicky, May 28 2022

a(8) and beyond from Michael S. Branicky, May 28 2022

cp's OEIS Frontend

A048458 'Prime last odd terms' from generation 2 onwards.

Views

Author

Keywords

Comments

Links

Crossrefs

Extensions