

A075190


Numbers n such that n^2 is an interprime = average of two successive primes.


25



2, 3, 8, 9, 12, 15, 18, 21, 25, 33, 41, 51, 60, 64, 72, 78, 92, 112, 117, 129, 138, 140, 159, 165, 168, 172, 192, 195, 198, 213, 216, 218, 228, 237, 273, 295, 298, 303, 304, 309, 322, 327, 330, 338, 342, 356, 360, 366, 387, 393, 408, 416, 429, 432, 441, 447, 456
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OFFSET

1,1


COMMENTS

Interprimes are in A024675, even interprimes are in A072568, odd interprimes are in A072569 n^3 as interprimes are in A075191, n^4 as interprimes are in A075192, n^5 as interprimes are in A075228, n^6 as interprimes are in A075229, n^7 as interprimes are in A075230, n^8 as interprimes are in A075231, n^9 as interprimes are in A075232, n^10 as interprimes are in A075233, a(n) such that a(n)^n = smallest interprime (of the form a^n) are in A075234.


LINKS

Zak Seidov, Table of n, a(n) for n=1..1317, a(n)<20000


FORMULA

a(n)=sqrt(A069495(n)). (Zak Seidov)


EXAMPLE

3 is a member because 3^2 = 9 is the average of two successive primes 7 and 11.


MAPLE

s := 2: for n from 2 to 1000 do if prevprime(n^s)+nextprime(n^s)=2*n^s then print(n) else; fi; od;


MATHEMATICA

PrevPrim[n_] := Block[{k = n  1}, While[ !PrimeQ[k], k ]; k]; NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; Select[ Range[464], 2#^2 == PrevPrim[ #^2] + NextPrim[ #^2] &] (* Robert G. Wilson v, Sep 14 2002 *)
n2ipQ[n_]:=Module[{n2=n^2}, (NextPrime[n2]+NextPrime[n2, 1])/2==n2]; Select[Range[500], n2ipQ] (* Harvey P. Dale, May 04 2011 *)
Select[Sqrt[Mean[#]]&/@Partition[Prime[Range[30000]], 2, 1], IntegerQ] (* Harvey P. Dale, May 26 2013 *)


CROSSREFS

Cf. A024675, A072568, A072569, A075190, A075191, A075192.
Cf. A075228, A075229, A075230, A075231, A075232, A075234.
Sequence in context: A283618 A284370 A273783 * A224225 A283160 A281148
Adjacent sequences: A075187 A075188 A075189 * A075191 A075192 A075193


KEYWORD

nonn


AUTHOR

Zak Seidov, Sep 09 2002


EXTENSIONS

Edited by Robert G. Wilson v, Sep 14 2002


STATUS

approved



