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A097639 a(n) is the smallest number m such that for the n-digit number s=10^(n-1)+ m, 10*s+1, 10*s+3, 10*s+7 and 10*s+9 are primes. 1
0, 0, 48, 300, 111, 234, 1395, 546, 2526, 5742, 753, 12369, 5658, 94572, 6744, 134649, 32523, 43071, 213927, 256116, 8172, 431904, 57138, 433125, 123225, 711447, 318501, 40758, 150063, 184602, 134661, 377778, 129048, 504678, 88113, 3174738 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n)=A097638(n)-10^(n-1). a(50)= 10718757, can you find a(100)?

LINKS

Table of n, a(n) for n=1..36.

FORMULA

a[n_]:=(For[m=0, !(PrimeQ[10^n+10m+1]&&PrimeQ[10^n+10m+3]&&PrimeQ [10^n+10m+7]&&PrimeQ[10^n+10m+9]), m++ ];m);

EXAMPLE

a(4)=300 because 10(10^3+300)+ 1, 10(10^3+300)+ 3,10(10^3+300)+ 7 &

10(10^3+300)+1, are primes and 300 is the smallest number with

this property.

MATHEMATICA

a[n_]:=(For[m=0, !(PrimeQ[10^n+10m+1]&&PrimeQ[10^n+10m+3]&&PrimeQ[ 10^n+10m+7]&&PrimeQ[10^n+10m+9]), m++ ]; m); Table[a[n], {n, 43}]

CROSSREFS

Cf. A097638, A007811.

Sequence in context: A173121 A281234 A215262 * A222773 A211732 A211743

Adjacent sequences:  A097636 A097637 A097638 * A097640 A097641 A097642

KEYWORD

base,nonn

AUTHOR

Farideh Firoozbakht, Aug 18 2004

STATUS

approved

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Last modified September 17 06:16 EDT 2021. Contains 347478 sequences. (Running on oeis4.)