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Search: id:A111054
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| A111054 |
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Sum of squares of digits of decimal expansion of square root of 2. |
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+0
1
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| 1, 17, 18, 34, 38, 39, 48, 73, 109, 113, 122, 171, 180, 180, 261, 286, 286, 302, 366, 430, 430, 431, 467, 531, 595, 644, 648, 664, 668, 668, 749, 785, 866, 930, 930, 979, 1043, 1068, 1104, 1185, 1221, 1270, 1271, 1335, 1384, 1409, 1418, 1467, 1503, 1584
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n) is prime for n = 2, 8, 9, 10, 22, 23, 46, ... a(n) is semiprime for n = 4, 5, 6, 11, 18, 31, 32, 33, 36, 37, 43, 47, ... a(n) is a perfect power for n = 1, 4, ...
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FORMULA
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a(n) = sum(i=1 to n) A002193(i)^2.
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EXAMPLE
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a(1) = 1^2 = 1,
a(2) = 1^2 + 4^2 = 17, which is prime,
a(3) = 1^2 + 4^2 + 1^2 = 18,
a(4) = 1^2 + 4^2 + 1^2 + 4^2 = 36,
a(10) = 1^2 + 4^2 + 1^2 + 4^2 + 2^2 + 1^2 + 3^2 + 5^2 + 6^2 + 2^2 = 113, which is prime.
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CROSSREFS
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Cf. A002193, A111033, A111034.
Adjacent sequences: A111051 A111052 A111053 this_sequence A111055 A111056 A111057
Sequence in context: A043870 A098159 A018821 this_sequence A022107 A041584 A041586
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Oct 06 2005
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