OFFSET
1,1
REFERENCES
D. Wells, Curious and interesting numbers, Penguin Books.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
14 and 15 because both have 4 as number of divisors and are consecutive.
MATHEMATICA
Union[Flatten[Select[Partition[Range[500], 2, 1], DivisorSigma[0, First[#]] == DivisorSigma[0, Last[#]]==4&]]] (* Harvey P. Dale, Jul 22 2012 *)
SequencePosition[DivisorSigma[0, Range[500]], {4, 4}]//Flatten//Union (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 15 2016 *)
PROG
(PARI) isA038456(n) = (numdiv(n)==4) && ((numdiv(n+1)==4) || (numdiv(n-1)==4)) \\ Michael B. Porter, Feb 03 2010
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected and extended by Olivier Gérard
Corrected by Rick L. Shepherd, Jun 07 2002
STATUS
approved