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

Author

N. J. A. Sloane, Aug 28 2022

Keywords

• nonn

Examples

			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.
		

Links

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

Crossrefs

Cf. A354790, A354791, A354792.