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Search: id:A119742
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| 1, 112, 293, 18474, 1026475, 2207286, 4088167, 5970048, 106081049, 206969050, 315070851, 425181862, 536191973, 647373084, 766191895, 946292976, 1127404157, 1309292338, 1497303219, 1686192100, 11694372101, 21776190102
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OFFSET
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1,2
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COMMENT
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Tetradic primes are primes that are palindromes and use only the digits 0, 1 and 8, so they read the same backwards and upside down. a(1) = 11, a(3) = 293 and a(21) = 11694372101 are primes.
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LINKS
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Eric Weisstein's World of Mathematics, Tetradic Number.
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FORMULA
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a(n) = SUM[i=1..n] A068188(i). a(n) = SUM[i=1..n] {A006072(k) such that A006072(k) is in A000040}.
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EXAMPLE
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a(21) = 11 + 101 + 181 + 18181 + 1008001 + 1180811 + 1880881 + 1881881 + 100111001 + 100888001 + 108101801 + 110111011 + 111010111 + 111181111 + 118818811 + 180101081 + 181111181 + 181888181 + 188010881 + 188888881 + 10008180001 = 11694372101.
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CROSSREFS
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Cf. A000040, A006072, A068188.
Sequence in context: A095615 A061281 A119684 this_sequence A154063 A047631 A008430
Adjacent sequences: A119739 A119740 A119741 this_sequence A119743 A119744 A119745
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KEYWORD
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base,easy,nonn,less
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Jun 16 2006
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