A355897 a(n) = index in A354790 of first nonprime term divisible by prime(n).

7, 7, 14, 14, 15, 17, 29, 64, 71, 79, 119, 120, 127, 223, 239, 260, 287, 288, 319, 320, 447, 484, 511, 512, 519, 960, 967, 968, 969, 1044, 1151, 1152, 1155, 1156, 1279, 1280, 1283, 1387, 1791, 1792, 1919, 1920, 1921, 2048, 2051, 2052, 2079, 3872, 3875, 3876, 3879, 3880, 4095, 4096

Offset

1,1

Links

N. J. A. Sloane, Table of n, a(n) for n = 1..236

Example

The first few nonprime terms in B = A354790, and their prime factors are:
    n  B(n)=p*q   p     pi(p)     q     pi(q)
    7,   6,       2,      1,      3,      2
   14,   35,      5,      3,      7,      4
   15,   22,      2,      1,      11,     5
   17,   39,      3,      2,      13,     6
   29,   85,      5,      3,      17,     7
   31,   14,      2,      1,      7,      4
   35,   33,      3,      2,      11,     5
B(14) = A354790(14) = 35 = 5*7 is the first nonprime term divisible by 5 = prime(3), therefore a(3) = 14.

Crossrefs

Cf. A354790, A354791, A354792.

Sequence in context: A173314 A040043 A339706 * A003872 A168374 A112438

Adjacent sequences: A355894 A355895 A355896 * A355898 A355899 A355900

Keyword

nonn

Author

N. J. A. Sloane, Aug 28 2022

Status

approved