OFFSET
1,1
LINKS
Muniru A Asiru, Table of n, a(n) for n = 1..10000
EXAMPLE
20 is abundant, 21, 22 and 23 are deficient, 24 is abundant.
36 is abundant, 37, 38 and 39 are deficient, 40 is abundant.
MAPLE
with(numtheory): A:=select(n->sigma(n)>2*n, [$1..800]): a:=seq(A[i], i in select(n->A[n+1]-A[n]=4, [$1..nops(A)-1]));
MATHEMATICA
q[n_] := DivisorSigma[1, n] > 2 n; Select[Range[704], q[#] && q[# + 4] && ! q[# + 1] && ! q[# + 2] && ! q[# + 3] &] (* Giovanni Resta, Jul 01 2018 *)
SequencePosition[Table[If[DivisorSigma[1, n]>2n, 1, 0], {n, 750}], {1, 0, 0, 0, 1}][[;; , 1]] (* Harvey P. Dale, Mar 02 2023 *)
PROG
(GAP) A:=Filtered([1..800], n->Sigma(n)>2*n);; a:=List(Filtered([1..Length(A)-1], i->A[i+1]-A[i]=4), j->A[j]);
CROSSREFS
KEYWORD
nonn
AUTHOR
Muniru A Asiru, Jun 25 2018
STATUS
approved