A146758 Last prime subtrahend at 10^n in A146757.

7, 97, 983, 9941, 99839, 999983, 9998239, 99999989, 999950881, 9999999929, 99999999833, 999999999989, 9999999999863, 99999999999971, 999999961946087, 9999999999999917, 99999999989350667, 999999999999999989

Offset

1,1

Links

Table of n, a(n) for n=1..18.

Example

A(2)=97 because 97 is the 15th and last prime difference under 10^2.

Maple

A146758 := proc(n) local p: p:=10^n: do p:=prevprime(p): if(isprime(ceil(evalf(sqrt(p)))^2-p))then return p: fi: od: end: seq(A146758(n), n=1..14); # Nathaniel Johnston, Oct 01 2011

Prog

(UBASIC) 10 'sq less pr are prime 20 N=1:O=1:C=1 30 A=3:S=sqrt(N):if N>10^3 then print N, C-1:stop 40 B=N\A 50 if B*A=N then 100 60 A=A+2 70 if A<=S then 40 80 R=O^2:Q=R-N 90 if N<R and N=prmdiv(N) and Q=prmdiv(Q) then if Q>1 print R; N; Q; C:N=N+2:C=C+1:goto 30 100 N=N+2:if N<R then 30:else O=O+1:goto 80

Crossrefs

Cf. A146757, A146759, A146760.

Sequence in context: A030540 A071361 A007810 * A114019 A178007 A241206

Adjacent sequences: A146755 A146756 A146757 * A146759 A146760 A146761

Keyword

more,nonn

Author

Enoch Haga, Nov 02 2008

Extensions

a(8)-a(18) from Nathaniel Johnston, Oct 01 2011

Status

approved