A204827 Deficient numbers with even sum of divisors.

3, 5, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 27, 29, 31, 33, 34, 35, 37, 38, 39, 41, 43, 44, 45, 46, 47, 51, 52, 53, 55, 57, 58, 59, 61, 62, 63, 65, 67, 68, 69, 71, 73, 74, 75, 76, 77, 79, 82, 83, 85, 86, 87, 89, 91, 92, 93, 94, 95, 97, 99, 101, 103

Offset: 1

Author

Jaroslav Krizek, Jan 22 2012

Keywords

• nonn

Comments

Numbers m from A005100 such that sigma(m) = A000203(m) is even.

Complement of A204826 with respect to A005100 (deficient numbers).

Examples

			Deficient number 15 is in sequence because sigma(15) = 24 (even number).
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• Eric Weisstein's World of Mathematics, Deficient Number

Crossrefs

Cf. A000203, A005100, A028983.

Cf. A156903 (abundant numbers with odd sum of divisors), A204825 (abundant numbers with even sum of divisors), A204826 (deficient numbers with odd sum of divisors).

Programs

Mathematica

dnesQ[n_]:=Module[{s=DivisorSigma[1,n]},s<2n&&EvenQ[s]]; Select[ Range[ 120],dnesQ] (* Harvey P. Dale, Nov 23 2014 *)