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 A187468 Sum of the squares modulo 2^n of the odd numbers less than 2^n. 2
 1, 2, 4, 40, 208, 928, 3904, 16000, 64768, 260608, 1045504, 4188160, 16764928, 67084288, 268386304, 1073643520, 4294770688, 17179475968, 68718690304, 274876334080, 1099508482048, 4398040219648, 17592173461504, 70368719011840, 281474926379008 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS There is a simple formula for this case; the sum of the squares of the odd numbers less than 2^n is A016131(n-1). Can the general case for m^n, m > 2 be calculated with a formula of the same kind? From R. J. Mathar, Aug 26 2013: (Start) For n>=3, the sum of the squares of the even numbers less than 2^n (each square mod 2^n) are 8 times the sequence 1, 2, 12, 56, 304, 1376, 6336, 27008 etc. and appear to obey a(n)= +6*a(n-1) -48*a(n-3) +64*a(n-4). For n>=1, the sum of the squares of the odd numbers less than 3^n (modulo 3^n) start as 2 times 1, 12, 144, 1404, 13689, 126360,.. and apparently obey a(n)= +12*a(n-1) -324*a(n-3) +729*a(n-4). For n>=1, the sum of the squares of the odd numbers less than 4^n (modulo 4^n) start as 2 times 1, 28, 688, 13504, 238336,... and seem to obey a(n)= +28*a(n-1) -224*a(n-2) +512*a(n-3). (End) LINKS Index entries for linear recurrences with constant coefficients, signature (6,-8). FORMULA For n>2 the sum of all r_j = (c_j)^2 mod 2^n for a particular n is given by [2^(n-1)]*[2^(n-1) - 3]. a(n) = 2^(n-2)*(2^n-6) for n>2. a(n) = 6*a(n-1)-8*a(n-2) for n>4. G.f.: x*(32*x^3-4*x+1) / ((2*x-1)*(4*x-1)). - Colin Barker, Aug 19 2013 EXAMPLE For n=5, 2^5=32. The c_j, numbers prime to 32 are the odd numbers less than 32.  The r_j = (c_j)^2 mod 32 are 1,9,25,17,17,25,9,1,1,9,25,17,17,25,9,1=4*52=208. From the formula, for n=5, [2^(5-1)]*[2^(5-1) - 3]=16*13=208; MATHEMATICA Join[{1, 2}, Table[2^(n - 1) (2^(n - 1) - 3), {n, 3, 20}]] CROSSREFS Sequence in context: A184952 A098337 A326483 * A238719 A158213 A012596 Adjacent sequences:  A187465 A187466 A187467 * A187469 A187470 A187471 KEYWORD nonn,easy AUTHOR J. M. Bergot, Mar 22 2011 EXTENSIONS Heavily edited by Olivier Gérard, Mar 23 2011 More terms from Colin Barker, Aug 19 2013 STATUS approved

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Last modified September 22 06:08 EDT 2020. Contains 337289 sequences. (Running on oeis4.)