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A225757 Table of consecutive numbers with the same sum of divisors. 3
14, 15, 206, 207, 957, 958, 1334, 1335, 1364, 1365, 1634, 1635, 2685, 2686, 2974, 2975, 4364, 4365, 14841, 14842, 18873, 18874, 19358, 19359, 20145, 20146, 24957, 24958, 33998, 33999, 36566, 36567, 42818, 42819, 56564, 56565, 64665, 64666, 74918, 74919, 79826 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Are 3 consecutive terms possible? There are none less than 10^12. See A002961. - T. D. Noe, May 15 2013

LINKS

T. D. Noe and Charles R Greathouse IV, Table of n, a(n) for n = 1..1000 (first 226 terms from Noe)

EXAMPLE

Sequence begins:

14, 15;

206, 207;

957, 958;

1334, 1335;

etc.

MATHEMATICA

sel = Select[Range[100000], DivisorSigma[1, #] == DivisorSigma[1, # + 1] &]; Union[sel, sel + 1]

Flatten[SequencePosition[DivisorSigma[1, Range[80000]], {x_, x_}]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 13 2017 *)

PROG

(PARI) v=List(); t=[1, 3]; for(n=3, 1e6, t=[t[2], sigma(n)]; if(t[1]==t[2], listput(v, n-1); listput(v, n))); vecsort(Vec(v), , 8) \\ Charles R Greathouse IV, May 15 2013

CROSSREFS

Cf. A225756 (same number of divisors), A225758 (same number and sum of divisors), A002961 (first number of each pair).

Sequence in context: A041412 A041414 A033050 * A041416 A041417 A041418

Adjacent sequences:  A225754 A225755 A225756 * A225758 A225759 A225760

KEYWORD

nonn,tabf

AUTHOR

Jean-François Alcover, May 15 2013

STATUS

approved

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Last modified March 28 20:44 EDT 2020. Contains 333103 sequences. (Running on oeis4.)