OFFSET
1,1
COMMENTS
EXAMPLE
41399193=3*11*101*12421; 101 = ((3^4)+(11^2))/2 and 12421 = ((11^4)+(101^2))/2, so 41399193 is a member.
MAPLE
n := 20: L := []: for a from 3 to n do if isprime(a) then for b from a to n^2 do if isprime(b) then c := (a^4+b^2)*(1/2); if isprime(c) then d := (b^4+c^2)*(1/2); if isprime(d) then L := [op(L), a*b*c*d]: end if end if end if end do end if end do; L := sort(L)
PROG
(PARI) factorsm(n)=my(v=factor(n), f=factor(n)[, 1]~, w=[]); for(i=1, #f, for(j=1, v[i, 2], w=concat(w, f[i]))); w;
is(n)=f=factorsm(n); if(#f==4, a=f[1]; b=f[2]; c=f[3]; d=f[4]; a<b&&b<c&&c<d&&c==((a^4)+(b^2))/2&&d==((b^4)+(c^2))/2, 0) \\ Anders Hellström, Aug 28 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
David Ferris, Aug 28 2015
STATUS
approved