A229254 Numbers k such that k and k+2 have the same number (A000005) and sum of divisors (A000203).

33, 54, 918, 1240, 3304, 4148, 4187, 7169, 12565, 15085, 19688, 24881, 25019, 26609, 38982, 51835, 53963, 59987, 76360, 77057, 96728, 143369, 150419, 167560, 170561, 205727, 215069, 220817, 278920, 418307, 564857, 731320, 785270, 907254, 910315, 986153

Offset: 1

Author

Jaroslav Krizek, Sep 20 2013

Keywords

• nonn

Comments

Also numbers k such that A229335(k) = A229335(k+2).

Intersection of A007373 and A062832.

Examples

			Divisors of 54 = {1, 2, 3, 6, 9, 18, 27, 54}, divisors of 56 = {1, 2, 4, 7, 8, 14, 28, 56}, both have 8 divisors and sum = 120.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A007373, A062832, A000005, A000203, A229335.

Programs

Mathematica

Select[Range[10000], DivisorSigma[0, #] == DivisorSigma[0, # + 2] && DivisorSigma[1, #] == DivisorSigma[1, # + 2] &]

PARI

isok(n) = (numdiv(n) == numdiv(n+2)) && (sigma(n) == sigma(n+2)); \\ Michel Marcus, Sep 20 2013

Extensions

More terms from Michel Marcus, Sep 20 2013