A092507 - OEIS

A092507

(Smallest prime >= 2^n) + (largest prime <= 2^n).

2, 4, 8, 18, 30, 68, 128, 258, 508, 1030, 2052, 4092, 8192, 16400, 32792, 65520, 131058, 262172, 524286, 1048596, 2097156, 4194312, 8388620, 16777210, 33554472, 67108860, 134217738, 268435446, 536870858, 1073741832, 2147483616

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OFFSET

0,1

COMMENTS

For n=0 we just take a(0)=2, the least prime >= 2^0, as there is no prime <= 2^0. - Robert Israel, Nov 01 2018

LINKS

Robert Israel, Table of n, a(n) for n = 0..3317

FORMULA

a(n) = A014210(n) + A014234(n) for n >= 2. - Robert Israel, Nov 01 2018

MAPLE

[2, seq( (nextprime(2^x-1)+prevprime(2^x+1)), x=1..20)]; # Corrected by Robert Israel, Nov 01 2018

MATHEMATICA

PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; Table[PrevPrim[2^n+1] + NextPrim[2^n-1], {n, 31}] (* Robert G. Wilson v, Apr 14 2004 *)

CROSSREFS

Cf. A014210, A014234, A058249.

Sequence in context: A351471 A229718 A246469 * A347036 A297188 A291583

Adjacent sequences: A092504 A092505 A092506 * A092508 A092509 A092510

KEYWORD

nonn

AUTHOR

Jorge Coveiro, Apr 05 2004

EXTENSIONS

More terms from Robert G. Wilson v, Apr 14 2004

STATUS

approved