login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A146760 Last prime subtrahend at 10^n in A146759. 4
5, 61, 997, 9929, 97283, 999983, 9999973, 99897341, 999999929, 9993948257, 99999999761, 999999999989, 9999516957181, 99999999999929, 999999999999989, 9999999999998857, 99999429057832259, 999999999999999989, 9999990391470218071 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It is not necessary to compute A146759 to compute this sequence. a(n) is the largest prime p<=10^n such that c(p)-p is also a prime, where c(p) is the smallest cube exceeding p. - Sean A. Irvine, Mar 27 2013

LINKS

Sean A. Irvine, Table of n, a(n) for n = 1..150

EXAMPLE

A(2)=61 because 61 is the 7th and last prime subtrahend under 10^3.

PROG

(UBASIC)

10 'cu 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^3: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. A146756, A146757, A146759.

Sequence in context: A012167 A162167 A134282 * A294024 A083082 A213110

Adjacent sequences:  A146757 A146758 A146759 * A146761 A146762 A146763

KEYWORD

easy,nonn

AUTHOR

Enoch Haga, Nov 02 2008

EXTENSIONS

More terms from Sean A. Irvine, Mar 27 2013

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 3 05:05 EST 2021. Contains 349445 sequences. (Running on oeis4.)