A164931 -id:A164931 - cp's OEIS frontend

A090178 a(1) = 2; for n > 1, a(n) = n + prime(n-1).

2, 4, 6, 9, 12, 17, 20, 25, 28, 33, 40, 43, 50, 55, 58, 63, 70, 77, 80, 87, 92, 95, 102, 107, 114, 123, 128, 131, 136, 139, 144, 159, 164, 171, 174, 185, 188, 195, 202, 207, 214, 221, 224, 235, 238, 243, 246, 259, 272, 277, 280, 285, 292, 295, 306, 313, 320, 327

Offset: 1

Pab Ter (pabrlos(AT)yahoo.com), May 29 2004

nonn

Sum of index n and the corresponding n-th term of noncomposite numbers (A008578).
Does n > 2 exist such that n*prime(n-1)/(n+prime(n-1)), i.e., A164931(n)/a(n) is an integer? - Jaroslav Krizek, Aug 31 2009
Complement of A171508(n). - Jaroslav Krizek, Dec 13 2009

			a(2) = 2 + prime(1) = 4; a(5) = 5 + prime(4) = 12; a(9) = 9 + prime(8) = 28.

M. Feenstra, P. J. Carter and C. P. Harding, The Ultimate I.Q. Book, Wardlock, see p. 99.

The published version (A048171) is said to be incorrect.

[n + NthPrime(n-1): n in [1..58] ]; // Klaus Brockhaus, Sep 09 2009

Join[{2}, Table[Prime[n - 1] + n, {n, 2, 60}]] (* Vincenzo Librandi, Dec 08 2015 *)

a(n) = n + A008578(n). - David Wasserman, May 20 2008

a(1) = 2; a(n) = 1 + A014688(n-1), for n >= 2. - Omar E. Pol, Nov 01 2013

Definition corrected, second comment and example edited by Klaus Brockhaus, Sep 09 2009

A171519 a(n) = numbers m such that are not the product of k-th noncomposite number and k for any k >= 1.

Original entry on oeis.org

2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55

Offset: 1

Jaroslav Krizek, Dec 11 2009

nonn

Complement of set {A(noncomposite number(n)*n)} = {A164931(n)} = {A(A008578(n)*A000027(n))}.

A372054 a(0)=1; thereafter a(n) = (n+1)*prime(n)+1.

Original entry on oeis.org

1, 5, 10, 21, 36, 67, 92, 137, 172, 231, 320, 373, 482, 575, 646, 753, 902, 1063, 1160, 1341, 1492, 1607, 1818, 1993, 2226, 2523, 2728, 2885, 3104, 3271, 3504, 4065, 4324, 4659, 4866, 5365, 5588, 5967, 6358, 6681, 7094, 7519, 7784, 8405, 8686, 9063, 9354, 10129, 10928, 11351

Offset: 0

N. J. A. Sloane, Apr 22 2024, based on messages from Thomas Scheuerle and Paul D. Hanna

nonn

Michael De Vlieger, Table of n, a(n) for n = 0..10000

{1}~Join~Array[(# + 1)*Prime[#] + 1 &, 49] (* Michael De Vlieger, Apr 22 2024 *)

a(n) = 1+A164931(n+1). - R. J. Mathar, Apr 24 2024

cp's OEIS Frontend

A090178 a(1) = 2; for n > 1, a(n) = n + prime(n-1).

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A171519 a(n) = numbers m such that are not the product of k-th noncomposite number and k for any k >= 1.

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A372054 a(0)=1; thereafter a(n) = (n+1)*prime(n)+1.

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