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A118667
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a(n) = a(n-1)+ ((abs(2^a(n-1)*a(n-1)) mod 10).
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0
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0, 1, 3, 7, 13, 19, 21, 23, 27, 33, 39, 41, 43, 47, 53, 59, 61, 63, 67, 73, 79, 81, 83, 87, 93, 99, 101, 103, 107, 113, 119, 121, 123, 127, 133, 139, 141, 143, 147, 153, 159, 161, 163, 167, 173, 179, 181, 183, 187, 193, 199, 201, 203, 207, 213, 219, 221, 223, 227, 233
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Apart from the first two terms all the other numbers can be formed adding in sequence 2, 4, 6, 6, 2 and so on. Example 1+(2)=3; 3+(4)=7; 7+(6)=13; 13+(6)=19; 19+(2)=21; ...
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FORMULA
| a(n) = a(n-1)+ ((abs(2^a(n-1)*a(n-1)) mod 10) being a(0) = 0 and a(1) = 1
a(n)=(2/5)*Sum{k=0..n-1}{3*(k mod 5)+[(k+1) mod 5]+[(k+4) mod 5]}-1+[C(2*n,n) mod 2], with n>=0 [From Paolo P. Lava (paoloplava(AT)gmail.com), Oct 07 2008]
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EXAMPLE
| a(2)= 1 + abs(2^1 *1)mod 10 = 1 + 2 mod 10 = 1 + 2 = 3
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MAPLE
| ANM:=proc(N) local an, i, anminus1, anplus1; anminus1:=0; an:=1; print (anminus1); print (an); for i from 2 by 1 to N do anplus1:=an+(abs(2^an*an) mod 10); print(anplus1); anminus1:=an; an:=anplus1; od; end: ANM(100);
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CROSSREFS
| Sequence in context: A045423 A032437 A076746 * A034017 A034021 A038978
Adjacent sequences: A118664 A118665 A118666 * A118668 A118669 A118670
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KEYWORD
| nonn
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AUTHOR
| Paolo P. Lava & Giorgio Balzarotti (paoloplava(AT)gmail.com), May 19 2006
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