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%I #8 Jan 27 2022 21:59:10
%S 2,2,3,2,4,10,1,7,4,4,4,9,8,8,8,4,1,4,7,5,5,3,5,5,2,4,7,4,1,8,8,6,-1,
%T 3,7,9,3,2,8,8,0,7,8,4,8,10,2,8,4,2,-1,6,7,3,-1,10,6,5,8,5,3,6,8,3,2,
%U 1,6,9,0,7,3,1,5,3,7,7,1,1,7,10,8,9,5,3,7,1,2,5,7,3,4,4,3,3,0,2,6,1,5,8,8
%N Alternately subtract and add 1 to digits in decimal expansion of Pi.
%H R. K. Hoeflin, <a href="http://www.eskimo.com/~miyaguch/ultra..html">Ultra Test</a>
%e a(1)= 3 - 1 = 2, a(2)= 1 + 1 = 2, a(3) = 4 - 1 = 3
%t Total/@Partition[Riffle[RealDigits[Pi,10,120][[1]],{-1,1},{2,-1,2}],2] (* _Harvey P. Dale_, Jan 20 2016 *)
%Y Cf. A000796.
%K easy,sign,base
%O 1,1
%A Anonymous, Feb 13 2000
%E More terms from _James A. Sellers_, Feb 22 2000