OFFSET
1,1
COMMENTS
The bi-unitary version of A096399.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
21735 is in the sequence since both 21735 and 21736 are bi-unitary abundant numbers.
MATHEMATICA
f[n_] := Select[Divisors[n], Function[d, CoprimeQ[d, n/d]]]; bsigma[m_] := DivisorSum[m, # &, Last@Intersection[f@#, f[m/#]] == 1 &]; bAbundantQ[n_] := bsigma[n] > 2 n; seq={}; n=1; While[Length[seq]<32, If[bAbundantQ[n] && bAbundantQ [n+1], AppendTo[seq, n]]; n++]; seq
PROG
(PARI) a188999(n) = {f = factor(n); for (i=1, #f~, p = f[i, 1]; e = f[i, 2]; f[i, 1] = if (e % 2, (p^(e+1)-1)/(p-1), (p^(e+1)-1)/(p-1) -p^(e/2)); f[i, 2] = 1; ); factorback(f); }
isok(n) = (a188999(n) > 2*n) && (a188999(n+1) > 2*(n+1)); \\ Michel Marcus, Aug 21 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Aug 20 2018
STATUS
approved