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A125002 Let p = prime(n); a(n) = number of primes q with same number of digits as p that can be obtained from p by changing one digit. 1
3, 3, 3, 3, 7, 8, 7, 7, 6, 5, 5, 5, 6, 7, 6, 6, 5, 5, 5, 6, 7, 6, 6, 5, 4, 10, 8, 11, 11, 6, 8, 9, 9, 10, 6, 7, 11, 9, 9, 8, 7, 6, 10, 9, 11, 9, 7, 8, 7, 6, 7, 7, 7, 7, 8, 9, 5, 7, 7, 7, 9, 6, 8, 6, 7, 8, 5, 8, 9, 6, 7, 6, 8, 7, 6, 8, 4, 8, 8, 10, 8, 6, 9, 6, 11, 5, 8, 7, 8, 8, 7, 7, 5, 8, 8, 5, 7, 5, 6, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

EXAMPLE

The 5th prime 11 leads to 7 other primes: 13,17,19,31,41,61,71, hence a(5)=7.

a(6)=8, p=13, q={11,17,19,23,43,53,73,83}

a(7)=7, p=17, q={11,13,19,37,47,67,97}

a(8)=7, p=19, q={11,13,17,29,59,79,89}

a(9)=6, p=23, q={29,13,43,53,73,83}

a(10)=5, p=29, q={23,19,59,79,89}

MAPLE

A125002 := proc(n) local p, digs, res, r, d; p := ithprime(n) ; digs := convert(p, base, 10) ; res := 0 ; for d from 1 to nops(digs) do for r from 0 to 9 do if r <> op(d, digs) and ( d <> nops(digs) or r > 0) then q := p-(op(d, digs)-r)*10^(d-1) ; if isprime(q) then res := res+1 ; fi ; fi ; od ; od ; RETURN(res) ; end ; for n from 1 to 100 do printf("%d, ", A125002(n)) ; od ; # R. J. Mathar, Jan 13 2007

PROG

(Haskell)

import Data.List (delete)

a125002 n = sum $ map (a010051' . read) $

                  tail $ concatMap (f pds) [0 .. length pds - 1] where

   pds = show $ a000040 n

   f ws k = [us ++ [y] ++ vs |

            let (us, v:vs) = splitAt k ws, y <- delete v "0123456789"]

-- Reinhard Zumkeller, Jul 06 2014

CROSSREFS

Cf. A000040.

Sequence in context: A339053 A244584 A092531 * A285245 A098528 A242715

Adjacent sequences:  A124999 A125000 A125001 * A125003 A125004 A125005

KEYWORD

nonn,base

AUTHOR

Zak Seidov, Jan 08 2007

EXTENSIONS

Corrected and extended by Hans Havermann and R. J. Mathar, Jan 08 2007

STATUS

approved

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Last modified April 11 23:19 EDT 2021. Contains 342895 sequences. (Running on oeis4.)