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A032352 Numbers n such that there is no prime between 10*n and 10*n+9. 31
20, 32, 51, 53, 62, 84, 89, 107, 113, 114, 126, 133, 134, 135, 141, 146, 150, 164, 167, 168, 171, 176, 179, 185, 189, 192, 196, 204, 207, 210, 218, 219, 232, 236, 240, 248, 249, 251, 256, 258, 282, 294, 298, 305, 309, 314, 315, 317, 323, 324, 326, 328 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n with property that appending any single decimal digit to n does not produce a prime.

A007920(n*10) > 10.

LINKS

M. I. Wilczynski, Table of n, a(n) for n = 1..10000

FORMULA

a(n) ~ n. - Charles R Greathouse IV, Mar 29 2013

EXAMPLE

m=32: 321=3*107, 323=17*19, 325=5*5*13, 327=3*109, 329=7*47, therefore 32 is a term.

MAPLE

a:=proc(n) if map(isprime, {seq(10*n+j, j=1..9)})={false} then n else fi end: seq(a(n), n=1..350); # Emeric Deutsch, Aug 01 2005

MATHEMATICA

f[n_] := PrimePi[10n + 10] - PrimePi[10n]; Select[ Range[342], f[ # ] == 0 &] (* Robert G. Wilson v, Sep 24 2004 *)

Select[Range[342], NextPrime[10 # ] > 10 # + 9 &] (* Maciej Ireneusz Wilczynski, Jul 18 2010 *)

PROG

(Haskell)

a032352 n = a032352_list !! (n-1)

a032352_list = filter

   (\x -> all (== 0) $ map (a010051 . (10*x +)) [1..9]) [1..]

-- Reinhard Zumkeller, Oct 22 2011

(MAGMA) [n: n in [1..350] | IsZero(#PrimesInInterval(10*n, 10*n+9))]; // Bruno Berselli, Sep 04 2012

(PARI) is(n)=!isprime(10*n+1) && !isprime(10*n+3) && !isprime(10*n+7) && !isprime(10*n+9) \\ Charles R Greathouse IV, Mar 29 2013

CROSSREFS

Cf. A124665 (subsequence), A010051, A007811, A216292, A216293.

Sequence in context: A116131 A212050 A075035 * A183048 A124665 A134989

Adjacent sequences:  A032349 A032350 A032351 * A032353 A032354 A032355

KEYWORD

nonn,base,easy

AUTHOR

Jeff Burch

EXTENSIONS

More terms from Miklos Kristof, Aug 27 2002

STATUS

approved

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Last modified November 20 04:05 EST 2017. Contains 294959 sequences.