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A340536 Digital root of 2*n^2. 0
2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9, 2, 8, 9, 5, 5, 9, 8, 2, 9 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Period 9: repeat [2, 8, 9, 5, 5, 9, 8, 2, 9].

This sequence is also right if digital root of factor in "2*n^2" is 2 (for example, "11*n^2", "20*n^2", "29*n^2", etc.)

LINKS

Table of n, a(n) for n=1..90.

Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,0,1).

FORMULA

a(n) = A010888(A001105(n)).

EXAMPLE

For n=5, 2*5^2 = 50 and digital root is 5, so a(5) = 5.

PROG

(PARI) dr(n) = if(n, (n-1)%9+1); \\ A010888

a(n) = dr(2*n^2); \\ Michel Marcus, Jan 21 2021

CROSSREFS

Cf. A001105, A010888, A056992.

Sequence in context: A179377 A199274 A140241 * A340778 A108744 A195724

Adjacent sequences:  A340533 A340534 A340535 * A340537 A340538 A340539

KEYWORD

nonn,base,easy

AUTHOR

Radaev Nikita, Jan 10 2021

STATUS

approved

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Last modified August 1 19:59 EDT 2021. Contains 346402 sequences. (Running on oeis4.)