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Search: id:A073641
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| A073641 |
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a(1) = 2; a(n) = smallest prime not included earlier such that concatenation of two successive terms is a prime. |
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3
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| 2, 3, 7, 19, 13, 61, 31, 37, 67, 79, 103, 43, 73, 127, 139, 97, 151, 157, 109, 199, 181, 193, 163, 211, 229, 223, 241, 271, 277, 331, 283, 397, 337, 313, 307, 367, 457, 421, 349, 373, 379, 433, 439, 409, 463, 523, 487, 601, 541, 547, 499, 571, 673, 613, 577
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Conjecture: every prime besides 5 is in this list. - Gabriel Cunningham (gcasey(AT)mit.edu), Apr 11 2003
It appears that terms belong to A007645[n] Cuban primes: of form x^2+xy+y^2; or: primes of form x^2+3*y^2; or: primes == 0 or 1 mod 3. There are no primes of form 6k-1 in this sequence. - Alexander Adamchuk (alex(AT)kolmogorov.com), Aug 15 2006
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FORMULA
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a(n) = A075609[n] for n>1. - Alexander Adamchuk (alex(AT)kolmogorov.com), Aug 15 2006
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CROSSREFS
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Cf. A075609.
Sequence in context: A005248 A032102 A100388 this_sequence A138111 A078373 A038878
Adjacent sequences: A073638 A073639 A073640 this_sequence A073642 A073643 A073644
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 09 2002
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EXTENSIONS
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More terms from Gabriel Cunningham (gcasey(AT)mit.edu), Apr 11 2003
Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 20 2003
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