A178615 Smaller of two consecutive numbers that are not the sum of 3 nonzero squares.

1, 4, 7, 15, 31, 39, 63, 79, 111, 127, 159, 207, 231, 239, 255, 319, 367, 399, 447, 495, 511, 519, 591, 623, 639, 751, 831, 879, 927, 959, 1007, 1023, 1135, 1263, 1279, 1359, 1391, 1471, 1519, 1599, 1647, 1775, 1791, 1903, 1983, 2031, 2047, 2079, 2159, 2287

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 30 2010

Keywords

• nonn

Comments

{1,2,4,5,7,8,10,13,15,16,20,23,25,28,31,32,..}->{1,4,7,15,31,..}

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A004214

Programs

Mathematica

q=66;q2=q^2+2;lst={};Do[Do[Do[z=a^2+b^2+c^2;If[z<=q2,AppendTo[lst,z]],{c,b,1,-1}],{b,a,1,-1}],{a,q}];lst; u=Union@lst;a=Complement[Range[q^2],u];lst={};Do[If[a[[n+1]]-a[[n]]==1,AppendTo[lst,a[[n]]]],{n,Length[a]-1}];lst