In this Letter we propose a simple algebraic recursion for the complete one-loop integrands of N-graviton correlators. This formula automatically yields the correct symmetry factors of individual diagrams, taking into account both the graviton and the ghost loop, and seamlessly controlling the related combinatorics.

Escuela de Matemáticas Universidad Nacional de Colombia Sede Medellín Carrera 65 59A 110 Medellín Colombia

Institute of Physics of the Czech Academy of Sciences and CEICO Na Slovance 2 18221 Prague Czech Republic

Universidad EIA C P 055428 Envigado Colombia

Universidad Santiago de Cali Facultad de Ciencias Basicas Calle 5 No 62 00 Barrio Pampalinda Cali Valle Colombia

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