A173596 The larger member of a near-repdigit emirp pair.

311, 733, 991, 1511, 1811, 3433, 3733, 7717, 7757, 16111, 79777, 99989, 112111, 333323, 334333, 733333, 778777, 787777, 911111, 999199, 1171111, 3733333, 9999299, 11131111, 11911111

Offset: 1

Author

Lekraj Beedassy, Feb 22 2010

Keywords

• base
• nonn

Comments

a(n) and an associated A173595 = A004086(a(n)) (not necessarily at the same position n) are a near-repdigit emirp pair, and all these pairs, sorted, generate A173594.

Crossrefs

Cf. A173594, A173595.

Programs

Maple

read("transforms") ; isA164937 := proc(n) local dse ; if isprime(n) and n > 100 then dse := convert(convert(n,base,10),multiset) ; if nops(dse) = 2 then op(2,op(1,dse)) = 1 and op(2,op(2,dse)) > 1 or op(2,op(1,dse)) > 1 and op(2,op(2,dse)) = 1; else false; end if ; else false; end if; end proc:
isA006567 := proc(n) if isprime(n) then pr := digrev(n) ; return isprime(pr) and pr <> n ; else false; end if; end proc:
isA173594 := proc(n) isA164937(n) and isA006567(n) ; end proc:
isA173596 := proc(n) return isA173594(n) and digrev(n) < n end proc:
for n from 2 do if isA173596(n) then printf("%d,",n) ; fi ; end do ; # R. J. Mathar, Mar 05 2010

Extensions

Keyword:base added by R. J. Mathar, Feb 24 2010, Mar 05 2010