A063729 Numbers k such that sigma(k)+1 is a square and sets a new record for such squares.
2, 7, 8, 14, 32, 54, 60, 72, 84, 120, 196, 252, 312, 378, 512, 540, 860, 990, 1020, 1350, 1488, 1560, 2190, 2232, 3084, 3144, 3288, 3444, 3456, 4620, 7740, 8520, 9720, 13080, 13500, 19230, 19590, 20088, 21120, 27090, 29064, 29232, 31500, 42336
Offset: 1
Keywords
Links
- Harry J. Smith, Table of n, a(n) for n = 1..150
Crossrefs
Cf. A063531.
Programs
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PARI
j=[]; for(n=1,70000,x=sigma(n)+1; if(issquare(x),b=x; if(b>a,a=b; \ j=concat(j,n)))); j
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PARI
{ n=0; a=-1; for (m=1, 10^9, if (issquare(b=sigma(m) + 1), if (b>a, a=b; write("b063729.txt", n++, " ", m); if (n==150, break))) ) } \\ Harry J. Smith, Aug 28 2009