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A176089
Numbers n such that 4(10^n-1)/9 * 10^ceiling(log_10(n+1)) + n is prime.
2
1, 547, 1187, 11183
OFFSET
1,2
COMMENTS
No term is a multiple of 2, 3, or 5. The decimal expansion of each corresponding prime is n 4's with n's decimal expansion concatenated. Probable primes found by PrimeForm. Primes for 547 and 1187 proved by Primo. No more terms up to 30000.
EXAMPLE
The first term is 1 because 41 is prime.
CROSSREFS
Cf. n k's followed by n is prime: A070746 (k=1), A176087 (k=3), A176090 (k=6), A084428 (k=7), A176091 (k=9). [k=2, 5, and 8 produce only composites divisible by 3.]
Sequence in context: A286440 A271448 A347203 * A261112 A219082 A123099
KEYWORD
more,nonn
AUTHOR
Rick L. Shepherd, Apr 11 2010
STATUS
approved