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A097638 a(n) is the smallest n-digit number m such that 10*m+1, 10*m+3, 10*m+7 & 10*m+9 are primes. 1
1, 10, 148, 1300, 10111, 100234, 1001395, 10000546, 100002526, 1000005742, 10000000753, 100000012369, 1000000005658, 10000000094572, 100000000006744, 1000000000134649, 10000000000032523, 100000000000043071 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) is the smallest n-digit term of A007811. a(50)=10^49+10718757, can you find a(100)?

LINKS

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

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++ ];10^(n-1)+m);

EXAMPLE

a(4)=1300 because 13001,13003,13007 & 13009 are primes and 1300 is the

smallest 4-digit 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++ ]; 10^(n-1)+m); Table[a[n], {n, 28}]

CROSSREFS

Cf. A097639, A007811.

Sequence in context: A055761 A295524 A095889 * A178084 A098270 A262738

Adjacent sequences:  A097635 A097636 A097637 * A097639 A097640 A097641

KEYWORD

base,nonn

AUTHOR

Farideh Firoozbakht, Aug 18 2004

STATUS

approved

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Last modified September 22 11:12 EDT 2021. Contains 347606 sequences. (Running on oeis4.)