A137831 a(n) = (prime(n)^2 minus its last digit)/20.

0, 0, 1, 2, 6, 8, 14, 18, 26, 42, 48, 68, 84, 92, 110, 140, 174, 186, 224, 252, 266, 312, 344, 396, 470, 510, 530, 572, 594, 638, 806, 858, 938, 966, 1110, 1140, 1232, 1328, 1394, 1496, 1602, 1638, 1824, 1862, 1940, 1980, 2226, 2486, 2576, 2622, 2714, 2856

Offset: 1

Author

Paul Curtz, Apr 29 2008

Keywords

• nonn
• base
• easy

Crossrefs

Cf. A001248, A137807.

Programs

Maple

a:= n-> iquo(ithprime(n)^2, 10)/2:
seq(a(n), n=1..52);  # Alois P. Heinz, Jun 03 2025

Mathematica

a[n_]:=(Prime[n]^2-Mod[Prime[n]^2,10])/20;Array[a,52] (* James C. McMahon, Jun 03 2025 *)

Formula

a(n) = (A001248(n)-A137807(n))/20. - R. J. Mathar, May 23 2008

Extensions

More terms from R. J. Mathar, May 23 2008