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 A342388 Integers y corresponding to the terms of A342387. 2
 6, 55, 474, 9360, 80029, 355452, 684228, 512562258, 986657022, 4382255359, 37466984190, 739114421304, 6319209189385, 54027365220036, 9112295268838531, 40472427468293976, 77907423180308442, 346027256676968725, 58361212342395772530, 498971064164650006699, 4266054677084570952198 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Chai Wah Wu, Table of n, a(n) for n = 1..950 Josep M. Brunat and Joan-Carles Lario, A problem on concatenated integers, arXiv:2103.05306 [math.NT], 2021. EXAMPLE y=6 is a term with x=20 because 7/21 = 207/621. PROG (PARI) isok(x) = {for (y=1, x-1, if ((y+1)/(x+1) == eval(Str(x, y+1))/eval(Str(y, x+1)), return (y)); ); } \\ A342387 for (x=1, 10000, if (y=isok(x), print1(y, ", "))) (Python) A342388_list, x, s1, s2, m = [], 1, '1', '2', 10 while x < 10**6: for y in range(1, x): if (x+1)*int(s1+str(y+1)) == (y+1)*(y*m+x+1): A342388_list.append(y) break x += 1 s1, s2 = s2, str(x+1) m = 10**(len(s2)) # Chai Wah Wu, Mar 10 2021 (Python) # based on formula in Brunat and Lario 2021 xlist, ylist, A342388_list, x, y = [4, 20, 39], [1, 6, 12], [6], 39, 12 while len(A342388_list) < 100: if len(str(x+1)) == len(str(y+1))+1: A342388_list.append(y) x, y = 19*xlist[-3]+60*ylist[-3]+39, 6*xlist[-3]+19*ylist[-3]+12 xlist, ylist = xlist[1:] + [x], ylist[1:] + [y] # Chai Wah Wu, Mar 10 2021 CROSSREFS Cf. A342387. Sequence in context: A295548 A198855 A318592 * A253475 A215853 A110431 Adjacent sequences: A342385 A342386 A342387 * A342389 A342390 A342391 KEYWORD nonn,base AUTHOR Michel Marcus, Mar 10 2021 EXTENSIONS More terms from Chai Wah Wu, Mar 10 2021 STATUS approved

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Last modified June 8 14:02 EDT 2023. Contains 363165 sequences. (Running on oeis4.)