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A112677
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Sum of digits of the sum of the previous 4 terms.
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1
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1, 1, 1, 1, 4, 7, 4, 7, 4, 4, 10, 7, 7, 10, 7, 4, 10, 4, 7, 7, 10, 10, 7, 7, 7, 4, 7, 7, 7, 7, 10, 4, 10, 4, 10, 10, 7, 4, 4, 7, 4, 10, 7, 10, 4, 4, 7, 7, 4, 4, 4, 10, 4, 4, 4, 4, 7, 10, 7, 10, 7, 7, 4, 10, 10, 4, 10, 7, 4, 7, 10, 10, 4, 4, 10, 10, 10, 7, 10, 10, 10, 10
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OFFSET
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0,5
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COMMENTS
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This is to the tetranacci sequence as A112661 is to the tribonacci and as A030132 is to Fibonacci. A000288 is the tetranacci sequence (A000078) but starting with values (1,1,1,1). Andrew Carmichael Post (andrewpost(AT)gmail.com) wrote the program that generated this sequence and showed that for any 4 initial integers a(0),a(1),a(2),a(3) the length of the cycle eventually entered is a factor of 312. For instance, starting with (6,6,6,6) continues in a cycle of length 1 since SOD(6+6+6+6) = SOD(24) = 6; and 1 divides 312. For the SOD(tribonacci) which is A112661, the length of any cycle eventually entered is a factor of 78.
All terms for n >= 4 are 4, 7, or 10. The sequence has period 78; the 78 terms after the initial 1,1,1,1 repeat forever. - Nathaniel Johnston, May 04 2011
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LINKS
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Table of n, a(n) for n=0..81.
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FORMULA
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a(0)=a(1)=a(2)=a(3)=1. a(n) = SumDigits(a(n-1)+a(n-2)+a(n-3)+a(n-4)). a(n) = SumDigits(A000288(n)).
a(n) = A007953(a(n-1) + a(n-2) + a(n-3) + a(n-4)). - Nathaniel Johnston, May 04 2011
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EXAMPLE
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a(0)=a(1)=a(2)=a(3)=1.
a(4) = SOD(1+1+1+1) = SOD(4) = 4.
a(5) = SOD(1+1+1+4) = SOD(7) = 7.
a(10) = SOD(4+7+4+4) = SOD(19) = 10, note that we do not iterate SOD to reduce 10 to 1.
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MAPLE
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A112677 := proc(n) option remember: if(n<=3)then return 1:fi: return add(d, d=convert(procname(n-1) + procname(n-2) + procname(n-3) + procname(n-4), base, 10)): end: seq(A112677(n), n=0..100); # Nathaniel Johnston, May 04 2011
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CROSSREFS
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Cf. A000078, A000288, A004090, A007953, A010888, A030132, A112661.
Sequence in context: A202501 A195362 A106739 * A010712 A081884 A059143
Adjacent sequences: A112674 A112675 A112676 * A112678 A112679 A112680
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jonathan Vos Post, Dec 30 2005
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EXTENSIONS
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Name corrected by Nathaniel Johnston, May 04 2011
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STATUS
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approved
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