OFFSET
1,1
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..2048 from Robert Israel)
EXAMPLE
135 is a member as 135 = 5*3^3 and 136 = 17*2^3.
MAPLE
with(numtheory):for n from 1 to 55000 do:x:=factorset(n):y:=factorset(n+1):x2:=sqrt(n):y2:=sqrt(n+1):n1:=nops(x):n2:=nops(y):if n1=2 and n2=2 and bigomega(n) = 4 and bigomega(n+1) = 4 and x2<>floor(x2) and y2<>floor(y2) then printf("%a, ", n):else fi:od:
# Alternative:
N:= 10^5: # to get all terms < N
P1:= select(isprime, {2, seq(2*i+1, i=1..floor(N/16))}):
P2:= select(t -> t^3 <= N/2, P1):
B:= {seq(seq(p^3*q, q=select(`<`, P1, floor(N/p^3)) minus {p}), p=P2)}:
B intersect map(`-`, B, 1); # Robert Israel, Jun 15 2014
MATHEMATICA
lst={}; Do[f1=FactorInteger[n]; If[Sort[Transpose[f1][[2]]]=={1, 3}, f2=FactorInteger[n+1]; If[Sort[Transpose[f2][[2]]]=={1, 3}, AppendTo[lst, n]]], {n, 3, 55000}]; lst
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Aug 05 2012
STATUS
approved