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A111054 Sum of squares of digits of decimal expansion of square root of 2. 0
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; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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, ...

LINKS

Table of n, a(n) for n=1..50.

FORMULA

a(n) = sum(i=1 to n) A002193(i)^2.

EXAMPLE

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.

CROSSREFS

Cf. A002193, A111033, A111034.

Sequence in context: A255923 A226673 A151978 * A242975 A155561 A231505

Adjacent sequences:  A111051 A111052 A111053 * A111055 A111056 A111057

KEYWORD

base,easy,nonn

AUTHOR

Jonathan Vos Post, Oct 06 2005

STATUS

approved

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Last modified May 15 10:54 EDT 2021. Contains 343909 sequences. (Running on oeis4.)