This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A218044 Numbers of the form 2^k + prime, with k > 0. 1
 4, 5, 6, 7, 9, 10, 11, 13, 15, 17, 18, 19, 21, 23, 25, 27, 29, 31, 33, 34, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 66, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A039669 is included in this sequence. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 P. Erdõs, On integers of the form 2^k + p and some related problems, Summa Brasil. Math. 2 (1950), pp. 113-123. Yong-Gao Chena and Xue-Gong Sunb, On Romanoff's constant, Journal of Number Theory, Volume 106, Issue 2, June 2004, Pages 275-284. N. P. Romanoff, Über einige Sätze der additiven Zahlentheorie, Math. Ann. 57 (1934) 668-678. EXAMPLE 5 = 3 + 2 that is, a prime and a power of 2. MATHEMATICA nn = 119; ps = Prime[Range[PrimePi[nn]]]; p2 = 2^Range[Log[2, nn]]; u = {}; Do[u = Union[u, ps + p2[[i]]], {i, Length[p2]}]; Select[u, # <= nn &] (* T. D. Noe, Oct 19 2012 *) PROG (PARI) isok(n) = {forprime(p=2, n, my(d = n - p); if ((d==2) || (ispower(d, , &k) && (k==2)), return(1)); ); 0; } \\ Michel Marcus, Apr 18 2016 CROSSREFS Cf. A080340, A039669, A118955 (allows k=0). Sequence in context: A242337 A201739 A329782 * A066485 A079445 A120173 Adjacent sequences:  A218041 A218042 A218043 * A218045 A218046 A218047 KEYWORD nonn,easy AUTHOR Michel Marcus, Oct 19 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 11 18:34 EST 2019. Contains 329925 sequences. (Running on oeis4.)