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

1,1

Comments

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

Intersection of A007373 and A062832.

Links

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

Example

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.

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A261107 A211141 A007373 * A242957 A024628 A061864

Adjacent sequences: A229251 A229252 A229253 * A229255 A229256 A229257

Keyword

nonn

Author

Jaroslav Krizek, Sep 20 2013

Extensions

More terms from Michel Marcus, Sep 20 2013

Status

approved