A181758 Greatest prime closest to n^3.

2, 7, 29, 67, 127, 211, 347, 509, 727, 997, 1327, 1733, 2203, 2741, 3373, 4099, 4909, 5827, 6857, 7993, 9257, 10651, 12163, 13829, 15629, 17579, 19681, 21961, 24391, 26993, 29789, 32771, 35933, 39301, 42863, 46663, 50651, 54869, 59333, 63997, 68917, 74093, 79493, 85193, 91127, 97327, 103813, 110597, 117643, 125003

Offset: 1

Author

Harvey P. Dale

Keywords

• nonn

Examples

			29 is the greatest prime closest to 3^3 = 27.
		

Links

• David A. Corneth, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A113426.

Programs

Mathematica

f3[n_]:=Module[{n3=n^3,np1,np2},np1=NextPrime[n3,-1];np2=NextPrime[n3];If[(n3-np1)<(np2-n3),np1,np2]];
Table[f3[i],{i,50}]

PARI

a(n) = {if(n == 1, return(1)); my(n3 = n^3, gp = nextprime(n^3), lp = precprime(n^3)); if(n3 - lp < gp - n3, return(lp) , return(gp) ) } \\ David A. Corneth, May 25 2021