A089537 -id:A089537 - cp's OEIS frontend

A085745 Numbers m such that 2^m + m is a semiprime.

2, 11, 23, 34, 59, 69, 87, 95, 119, 123, 129, 171, 197, 239, 341, 425, 455, 471, 515, 519, 635, 765, 959, 1115, 1181, 1210

Offset: 1

Jason Earls, Jul 21 2003

a(27) >= 1239. If 1239 is not a term then a(27) = 1275. - Amiram Eldar, Oct 26 2024

factordb, 2^1239+1239.

Cf. A006127, A052007, A089535, A089536, A089537.

Sequences A165767, A165768, A165769 are the analog for 2^n-n. - M. F. Hasler, Oct 08 2009

Select[Range[1300],PrimeOmega[2^#+#]==2&] (* Harvey P. Dale, Dec 18 2014 *)

a(n) = 2*k <=> A089535(n) is even <=> A089536(n) = 2 <=> A089537(n) = 4^k/2 + k, and for any prime of this form, there is a term a(n) = 2*k in this sequence. - M. F. Hasler, Oct 08 2009

More terms from Ray Chandler, Nov 08 2003
a(15) from Donovan Johnson, Mar 06 2008
a(16)-a(26) from Sean A. Irvine, Oct 27 2009
Offset changed to 1 by Jinyuan Wang, Jul 30 2021

A089535 Semiprimes of the form 2^k + k.

Original entry on oeis.org

6, 2059, 8388631, 17179869218, 576460752303423547, 590295810358705651781, 154742504910672534362390615, 39614081257132168796771975263, 664613997892457936451903530140172407, 10633823966279326983230456482242756731, 680564733841876926926749214863536423041

Offset: 1

Ray Chandler, Nov 08 2003

nonn

Amiram Eldar, Table of n, a(n) for n = 1..26

Intersection of A001358 and A006127.

Cf. A085745, A089536, A089537, 129962.

Select[Table[2^k+k,{k,200}],PrimeOmega[#]==2&] (* Harvey P. Dale, Aug 11 2024 *)

a(n) = 2^A085745(n) + A085745(n).

a(10)-a(11) from Jinyuan Wang, Jul 30 2021

A089536 Lesser prime factor of semiprimes in A089535.

Original entry on oeis.org

2, 29, 31, 2, 7, 7, 5, 1188359, 1307, 165864626101044727, 36120307175753, 9772772454840984668059, 8944440848667088469951, 3041407, 6446147951, 48370466980471484946806147635774599979591, 24025609733, 11, 15866068029777944368693, 50031370538856249715800928172618839

Offset: 1

Ray Chandler, Nov 08 2003

nonn

Amiram Eldar, Table of n, a(n) for n = 1..26

Cf. A020639, A085745, A089535, A089537.

a(n) = A020639(A089535(n)). - Michel Marcus, Jul 31 2021

a(n) = A089535(n)/A089537(n). - Amiram Eldar, Oct 26 2024

a(14) from Donovan Johnson, Sep 05 2008

Offset changed to 1 and more terms from Jinyuan Wang, Jul 30 2021

cp's OEIS Frontend

A085745 Numbers m such that 2^m + m is a semiprime.

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A089535 Semiprimes of the form 2^k + k.

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A089536 Lesser prime factor of semiprimes in A089535.

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